Compositions for sealing  an annulus of a wellbore

ABSTRACT

A sealing composition for sealing an annulus of a wellbore includes from 20 weight percent to 97 weight percent epoxy resin based on the total weight of the composition. The epoxy resin comprising at least one of 2,3-epoxypropyl o-tolyl ether, alkyl glycidyl ethers having from 12 to 14 carbon atoms, or a compound having formula (OC2H3)—CH2—O—R1—O—CH2—(C2H3O), where R1 is a linear or branched hydrocarbyl having from 4 to 24 carbon atoms. The sealing composition also includes from 1 weight percent to 20 weight percent curing agent based on the total weight of the composition.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a divisional application of U.S. patent applicationSer. No. 16/117,902, filed on Aug. 30, 2018, the entire contents ofwhich are incorporated by reference in this disclosure.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to naturalresource well drilling and, more specifically, to sealing compositionsand methods for sealing the wellbore annulus or casing-casing annuli ina wellbore.

BACKGROUND

Extracting subterranean hydrocarbon sources may require drilling a holefrom the surface to the subterranean geological formation housing thehydrocarbons. Specialized drilling techniques and materials are utilizedto form the bore hole and extract the hydrocarbons. Specializedmaterials utilized in drilling operations include materials for sealingthe casing-casing annulus of the wellbore, which may be formulated forspecific downhole conditions.

A wellbore is a hole that extends from the surface to a location belowthe surface to permit access to hydrocarbon-bearing subterraneanformations. The wellbore contains at least a portion of a fluid conduitthat links the interior of the wellbore to the surface. The fluidconduit connecting the interior of the wellbore to the surface may becapable of permitting regulated fluid flow from the interior of thewellbore to the surface and may permit access between equipment on thesurface and the interior of the wellbore.

The fluid conduit may be defined by one or more tubular strings havingat least two openings (typically on opposing ends) with an enclosingsurface having an interior and exterior surface. The interior surfaceacts to define the bounds of the fluid conduit. Examples of tubularstrings and portions of tubular strings used in the wellbore as fluidconduits or for making or extending fluid conduits include casing,production liners, coiled tubing, pipe segments, tubes, pipe strings,mechanical structures with interior voids, or combinations of these. Atubular string may include an assembly of several shorter tubularstrings connected to one another, such as joined pipe segments orcasing.

When positioning a tubular string or a portion of a tubular string inthe wellbore, the volume between the exterior surfaces of the tubularstring and the wellbore wall forms and defines a wellbore annulus. Thewellbore annulus has a volume in between the external surface of thetubular string and the wellbore wall. Additional casing-casing annulimay be formed by installing progressively smaller tubular strings withinthe larger tubular string initially secured in the wellbore. Installingeach tubular string includes positioning the tubular string in thewellbore and placing a sealing material in the wellbore annulus or thecasing-casing annulus to seal the annulus.

Primary sealing refers to the process of initially sealing the annulusupon installation of the casing or other tubular string and may refer toinitial sealing of the annulus between the exterior surface of thetubular string and the wellbore wall of the wellbore or initial sealingof a casing-casing annulus between two tubular strings installed in thewellbore. Primary sealing forms a protective solid sheath around theexterior surface of the tubular string. Primary sealing may anchor andsupport the tubular string in the wellbore and may protect the tubularstring from corrosion caused by fluids from the hydrocarbon-containingformation. Primary sealing may also provide a hydraulic seal in theannulus that may prevent migration of gases and liquids from one side ofthe solid sealing composition to the other. This hydraulic seal mayprevent fluid communication between production zones in the wellbore,referred to as zonal isolation, or may prevent migration of fluids tothe surface.

Primary sealing in conventional wellbore installations are performedwith cement compositions and, thus, may be commonly referred to as“primary cementing.” In conventional wellbore installations, the cementcomposition is pumped into the annulus and allowed to cure to form acement sheath around the exterior surface of the tubular string. Duringproduction, this cement sheath is subjected to temperature and pressurecycling. This temperature and pressure cycling may cause micro-cracks toform in the cement sheath. Fluids, such as gas or liquids, may migratethrough the micro-cracks, which may cause pressure buildup in theannuli, referred to as casing-casing annulus pressure. Increasingcasing-casing annulus pressure caused by micro-cracks in the cementsheath may cause damage to interior structures of the well, such asinterior casings and production liners. Greater casing-casing annuluspressure may also cause fluids to migrate through the cement sheath inthe annulus to the surface, where the fluids may be released to theenvironment. These effects of increasing casing-casing annulus pressureare even more pronounced in wells for hydrocarbon gases.

SUMMARY

Accordingly, there is a need for annulus sealing compositions that aremore resistant to formation of micro-cracks caused by thermal andpressure cycling of the wellbore. There is also a need for sealingcompositions that can be used to remediate existing wellboreinstallations that have developed micro-cracks and casing-casing annuluspressure increases.

This need is met by the present sealing composition embodiments, inwhich the sealing composition includes an epoxy resin system comprisingat least one epoxy resin and at least one curing agent. Once cured, thesealing composition comprising the epoxy resin system may form a barrierto prevent fluids, such as gases, liquids, or both, from penetratingthrough the annulus. The sealing composition may exhibit greatercompressive strength, reduced density, and greater elasticity comparedto conventional cement compositions, which may enable the sealingcomposition to resist degradation, such as formation of micro-cracks,caused by temperature and pressure cycling during production. Thesealing composition may, therefore, prevent penetration of fluids fromthe hydrocarbon-bearing formation through the sealing composition andmigration of these fluids to the surface or through the wellbore annulusor casing-casing annulus. The sealing compositions may be more resistiveto corrosive fluids than conventional cements. The sealing compositionsthat include the epoxy resin system can withstand greater pressures thanconventional cement, which may improve the zonal isolation and mitigategas migration through the sealing composition. For example, the sealingcompositions that include the epoxy resin system can withstand pressuresin a range of from 7,000 pounds per square inch (psi) to 15,000 psi thatare greater than conventional cement compositions, which can onlywithstand pressures in a range of from 500 psi to 5,000 psi. Thisability of the sealing compositions with the epoxy resin system towithstand greater pressures may enable the sealing compositions to beinjected deeper into high-pressure formations compared to conventionalcement compositions. Also, the epoxy resin system may be substantiallyfree of solids, which may make the sealing compositions that include theepoxy resin system attractive in low-injectivity zones whereconventional cement cannot be used. The sealing compositions having theepoxy resin system can be used for primary sealing as well as inremedial operations to provide effective zonal isolation or to repaircasing-casing annular leaks due to their ability to withstand increaseddifferential pressure.

According to some embodiments, a composition for sealing an annulus of awellbore may include from 20 weight percent to 97 weight percent epoxyresin based on the total weight of the composition, the epoxy resincomprising at least one of 2,3-epoxypropyl o-tolyl ether, alkyl glycidylethers having from 12 to 14 carbon atoms, or a compound having formula(I):

(OC₂H₃)—CH₂—O—R¹—O—CH₂—(C₂H₃O)  (I)

where R¹ is a linear or branched hydrocarbyl having from 4 to 24 carbonatoms. The composition may also include from 1 weight percent to 20weight percent curing agent based on the total weight of thecomposition.

According to other embodiments, a composition for sealing an annulus ofa wellbore may include from 20 weight percent to 97 weight percent epoxyresin based on the total weight of the composition, the epoxy resincomprising bisphenol-A-epichlorohydrin epoxy resin and a reactivediluent having formula R²—O—CH₂—(C₂H₃O), where R² is hydrocarbyl havingfrom 12 to 14 carbon atoms. The composition may also include from 1weight percent to 20 weight percent curing agent based on the totalweight of the composition.

According to still other embodiments, a method for sealing an annulus ofa wellbore may include introducing a spacer fluid into a tubular stringpositioned in the wellbore, the spacer fluid displacing at least aportion of a drilling fluid disposed in the wellbore and introducing asealing composition into the tubular string positioned in the wellboreto displace at least a portion of the spacer fluid. The sealingcomposition may include from 20 weight percent to 97 weight percentepoxy resin based on the total weight of the sealing composition, theepoxy resin comprising at least one of alkyl glycidyl ethers having from12 to 14 carbon atoms, 2,3-epoxypropyl o-tolyl ether, abisphenol-A-epichlorohydrin epoxy resin, or a compound having formula(I):

(OC₂H₃)—CH₂—O—R¹—O—CH₂—(C₂H₃O)  (I)

where R¹ is a hydrocarbyl having from 4 to 24 carbon atoms, where theepoxy resin has an epoxy equivalent weight of from 170 to 350 epoxyequivalents per gram. The sealing composition may also include from 1weight percent to 20 weight percent curing agent based on the totalweight of the sealing composition. The method may further includeintroducing a displacement fluid into the wellbore to transfer thesealing composition into an annulus of the well and curing the sealingcomposition.

In still other embodiments, a method for repairing a weak zone in ahydrocarbon production well may include perforating at least one tubularstring in the weak zone of the hydrocarbon production well and injectinga sealing composition through the tubular string and into the weak zoneof the hydrocarbon production well. The sealing composition may includefrom 20 weight percent to 97 weight percent epoxy resin based on thetotal weight of the sealing composition, the epoxy resin comprising atleast one of alkyl glycidyl ethers having from 12 to 14 carbon atoms,2,3-epoxypropyl o-tolyl ether, a bisphenol-A-epichlorohydrin epoxyresin, or a compound having formula (I):

(OC₂H₃)—CH₂—O—R¹—O—CH₂—(C₂H₃O)  (I)

where R¹ is a hydrocarbyl having from 4 to 24 carbon atoms, where theepoxy resin has an epoxy equivalent weight of from 170 to 350 epoxyequivalents per gram. The sealing composition may also include from 1weight percent to 20 weight percent curing agent based on the totalweight of the sealing composition. The method may further include curingthe sealing composition.

Additional features and advantages of the described embodiments will beset forth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the described embodiments, including thedetailed description which follows as well as the claims.

DETAILED DESCRIPTION

As used throughout this disclosure, the term “hydrocarbon-bearingformation” refers to a subterranean geologic region containinghydrocarbons, such as crude oil, hydrocarbon gases, or both, which maybe extracted from the subterranean geologic region.

As used throughout this disclosure, the term “fluid” may includeliquids, gases, or both. As used throughout the disclosure, “spacerfluid” refers to a fluid utilized to space apart any two other materialsutilized in well production.

Embodiments of the present disclosure are directed to sealingcompositions and methods of sealing the casing-casing annulus in awellbore using the sealing compositions. The sealing compositionincludes an epoxy system comprising an epoxy resin and a curing agent.In one embodiment, the sealing composition includes from 20 weightpercent (wt. %) to 97 wt. % epoxy resin and from 1 wt. % to 20 wt. %curing agent. The sealing composition may be introduced to the annulusof the wellbore and cured to seal the annulus between the outer casingand the wellbore wall or any of the casing-to-casing annuli. The sealingcomposition may also be introduced to a portion of the wellboreexperiencing casing-casing annulus pressure increase or damage caused byannulus pressure to remediate the portion of the wellbore.

Other embodiments of the present disclosure are directed to lostcirculation material (LCM) compositions and methods of remediating lostcirculation zones using the LCM compositions. The LCM compositionsinclude the prior described epoxy system comprising the epoxy resin andcuring agent. The LCM compositions may include from 50 weight percent(wt. %) to 97 wt. % epoxy resin and from 2 wt. % to 30 wt. % curingagent. The LCM composition may be introduced to a lost circulation zoneto isolate the lost circulation zone from the wellbore.

Once cured, the sealing compositions and LCM compositions act as abarrier to prevent fluids, such as liquids and gases, from migratingthrough the sealing composition or LCM composition to the surface orinto the production pipe of the well. Additionally, once cured, thesealing compositions and LCM compositions act as a barrier to preventfluids, such as drilling fluids, sealing compositions, or both, fromflowing from the wellbore into the subterranean formation and beinglost. Once cured, the epoxy resin system of the sealing composition andLCM composition may exhibit greater compressive strength, lesserdensity, and greater elasticity compared to conventional cementcompositions used for sealing the annuli of a wellbore or isolating lostcirculation zones. For example, adding an amount of the epoxy resinsystem to a conventional cement composition may increase a compressivestrength of the composition by at least 35% compared to the cementcomposition without the epoxy resin system. Regarding elasticity, insome embodiments, a sealing composition of the present disclosure mayhave a static bulk modulus of 1.184×10⁶ pounds per square inch (psi)which is less than the static bulk modulus of 1.404×10⁶ psi for aconventional hematite slurry (i.e., conventional cement composition).The static bulk modulus of a sealing composition is an elastic constantequal to the change in applied pressure divided by the ratio of thechange in volume to the original volume of a body. A lesser static bulkmodulus indicates greater elasticity.

These mechanical properties of the sealing composition and LCMcomposition may make the sealing composition and LCM composition lessbrittle and provide a greater deformation capacity compared toconventional cement compositions. In addition, the sealing compositionsthat include the epoxy resin system, prior to curing, may havebeneficial rheological properties to enable the sealing composition totransmit hydrostatic pressure to the formation during the primarysealing process to support the wellbore walls and prevent fluid flowfrom the subterranean hydrocarbon-bearing formation into the wellbore.The sealing composition incorporating the epoxy resin system can be usedin remedial operations to provide effective zonal isolation and torepair casing-casing annular leaks. As discussed subsequently in thisdisclosure, the sealing compositions and LCM compositions can beprepared with different density, viscosity, and mechanical properties bychanging the concentration of the epoxy resin or curing agent. Forexample, the sealing composition or LCM composition can be designed toproduce a final cured epoxy that is rigid or flexible, as needed. Thus,the epoxy resin system may be adapted for use in different downholeconditions of the wellbore.

Also, in some embodiments, the sealing compositions or LCM compositionsthat include the epoxy resin system may be substantially free of solids,which may make the sealing compositions and LCM compositions suitablefor low-injectivity zones, for which conventional cement compositionscannot be used. The sealing compositions and LCM compositions with theepoxy resin system may have reduced density compared to conventionalcement compositions, which makes the sealing composition more suitablefor narrow fracture pressure gradient zones compared to the conventionalcement compositions.

The wellbore forms a pathway capable of permitting both fluid andapparatus to traverse between the surface and the hydrocarbon-bearingformation. Besides defining the void volume of the wellbore, thewellbore wall also acts as the interface through which fluid cantransition between the formations through which the wellbore traversesand the interior of the well bore. The wellbore wall can be unlined(that is, bare rock or formation) to permit such interaction with theformation or lined (that is, with a tubular string as previouslydescribed in this disclosure) so as to not permit such interactions.

The wellbore contains at least a portion of a fluid conduit that linksthe interior of the wellbore to the surface. The fluid conduitconnecting the interior of the wellbore to the surface may be capable ofpermitting regulated fluid flow from the interior of the wellbore to thesurface and may permit access between equipment on the surface and theinterior of the wellbore. Example equipment connected at the surface tothe fluid conduit includes pipelines, tanks, pumps, compressors andflares. The fluid conduit may be large enough to permit introduction andremoval of mechanical devices, including but not limited to tools, drillstrings, sensors and instruments, into and out of the interior of thewell bore.

As previously described, the fluid conduit may be defined by a tubularstring installed in the wellbore. The wellbore annulus has a volumedefined between the external surface of the tubular string and thewellbore wall. As wellbore drilling continues and the wellbore extendsdeeper into the subterranean formation, one or more additional tubularstrings may be installed within the fluid conduit defined by the initialtubular string. Additional tubular strings may have outercross-sectional dimensions that are less than the inner cross-sectionaldimensions of the tubular strings within which the additional tubularstrings are disposed. Thus, the additional tubular string, wheninstalled in the wellbore, may form a casing-casing annulus definedbetween the exterior surface of the additional tubular string and theinterior surface of the tubular string surrounding the additionaltubular string. Therefore, after drilling is complete and the wellboreis fitted with production tubing for production, the wellbore maycomprise a plurality of tubular strings of progressively smallercross-sectional dimensions that form a wellbore annulus and a pluralityof casing-casing annuli.

As previously described in this disclosure, installing each tubularstring includes positioning the tubular string in the wellbore andprimary sealing the tubular string in the wellbore. The primary sealingprocess includes placing a sealing composition in the annulus and curingthe sealing composition to seal the annulus. Before primary sealing canbe performed, the wellbore may be drilled using a drill string in thepresence of a drilling fluid. At the conclusion of drilling, thewellbore is filled with drilling fluid. The drilling fluid is left inthe wellbore, and the tubular string is positioned in the wellbore. Whenthe tubular string is positioned in the wellbore, the drilling fluid mayfill the interior volume of the tubular string as well as the annulusbetween the exterior surface of the tubular string and the wellborewall. For interior tubular strings, the tubular string may form awellbore annulus between the exterior surface and the wellbore wallalong part of the length of the tubular string and a casing-casingannulus between the exterior surface and an interior surface of thepreviously installed casing along an uphole part of the length of thetubular string.

In some circumstances, the sealing composition may be incompatible withthe drilling fluid. Therefore, to commence primary sealing, a spacerfluid may first be pumped into the interior volume of the tubular stringto displace the drilling fluid and provide a buffer between the drillingfluid and the sealing composition. Various washing fluids or preflushfluids may also be introduced to the interior volume of the tubularstring before or after the spacer fluid. Washing fluids may be used toremove films and residue from the surfaces of the tubular string andwellbore wall. A fixed amount of the sealing composition may then bepumped into the internal volume of the tubular string after the spacerfluid. The fixed amount of the sealing composition may be an amount thatfills the annulus, such as the wellbore annulus, casing-casing annulus,or both. A downhole plug may be used between the spacer fluid andsealing composition, and an uphole plug may be inserted after thesealing composition.

A displacement fluid may be pumped into the interior volume of thetubular string after the uphole plug to force the sealing composition tothe downhole end of the tubular string, around the downhole edge of thetubular string, and into the annulus. A displacement fluid may also bereferred to as a flush fluid. The displacement fluid is pumped into theinterior volume of the tubular string until all of the sealingcomposition is disposed within the annulus. Cooperation of the downholeplug and uphole plug may operate to maintain the sealing composition inthe annulus.

The sealing composition may then be allowed to cure to form a sealingbarrier between the tubular string and the wellbore wall, between thetubular string and an outer tubular string, or both. When the sealingcomposition cures, the sealing composition physically and chemicallybonds with both the exterior surface of the tubular string and thewellbore wall or interior surface of the outer casing surrounding thetubular string, coupling the tubular string to the wellbore wall or theouter casing. This fluid isolation does not permit fluid migrationthrough the sealing composition to the interior of the well or uphole tothe surface.

In addition to primary sealing, remedial sealing may be performed usingthe sealing compositions. In remedial sealing, the sealing compositionis introduced to specific locations within the wellbore to repair thewellbore, such as to repair sections of the wellbore in whichmicro-cracks have formed in the annuli or in which increasedcasing-casing annulus pressure has caused damage to the tubular strings.Remedial sealing may also include injecting the sealing composition intothe wellbore for purposes of sealing the wellbore in preparation forabandonment. In some situations, remedial sealing may include theprocess of “squeezing,” in which the sealing composition is forcedagainst the inner surface of the portion of the well to be remediated,such as the inner surface of the innermost tubular string. As thesealing composition is forced against the inner surface of the tubularstring or wellbore wall, liquid portions of the sealing composition maybe “squeezed” into the microcracks, or into the formation in the case ofremediating the wellbore wall. For conventional sealing compositions,the solids may form a layer on the inner surface of the tubular string.

While drilling the wellbore, the drilling operation may encounter a lostcirculation zone. In a lost circulation zone, drilling fluid, sealingcompositions, or both flow from the wellbore into the subterraneanformation, resulting in loss of the drilling fluid or sealingcomposition from the drilling process. In some instances, lostcirculation may be caused by the natural state of the formation throughwhich the drilling passes. For example, the subterranean formation maybe naturally fractured or may be an unconsolidated formation, such asgravel, sand, pea, or other unconsolidated material. Alternatively, inother situations, the hydrostatic pressure of the drilling fluid orsealing composition may be greater than the fracture gradient of thesubterranean formation, which may cause the at least some breakdown ofthe pores in the formation. If the pores in the formation breakdownenough, then the pores become big enough to receive the fluids from thewellbore rather than resisting flow of these fluids.

Lost circulation zones may be remediated by introducing a material intothe formation in the lost circulation zone to seal the lost circulationzone from the wellbore. The material may be injected into the formationor squeezed into the formation. Conventional lost circulation materials(LCM) can include bridging material, fibrous material, flaky material,cement such as low-cure-time cement, and other materials havingdifferent particle sizes. Specific examples of conventional lostcirculation materials may include calcium carbonate, cements, paper,cottonseed hulls, nutshells, or other similar materials. These materialsmay be effective at mediating many lost circulation zones by forming alayer of solids over the formation at the lost circulation zone.However, these materials are not effective for use as LCM inlow-injectivity zones, because the solids content of these conventionalmaterials prevents these materials from being injected into theformation.

Low-injectivity zones are zones in which it is not possible to injectmaterials containing solid particles. Low-injectivity zones may includezones having an injectivity factor of greater than 4000 pounds of forceper square inch—min per barrel (psi-min/bbl), or even greater than 6000psi-min/bbl. As used herein, the term “barrel” refers to a unit ofmeasure equal to 42 U.S. Gallons. The injectivity factor is defined asthe quotient of the injection pressure in pounds of force per squareinch (psi) divided by the injection rate in barrels per minute(bbl/min). These low-injectivity zones may include, but are not limitedto, tight fractures comprising very narrow microcracks from the wellboreinto the subterranean formation and areas in which the annular distancebetween casings is tight. In low-injectivity zones, the average width ofthe microcracks in the formation or the annular distance between casingsmay be less than 100 microns, such as less than 50 microns, or even lessthan 10 microns. In these low-injectivity zones, solids particles in thecement composition or other material compositions may cause blockage andprevent cement or other compositions from being injected into the zone.For example, cement compositions and other conventional materials forremediating lost circulation zones include greater concentrations ofsolids and are not generally injectable into low-injectivity zones.Low-injectivity zones require the use of materials that aresubstantially free of solids or solid particles. As used in thisdisclosure, the term “substantially free” of a constituent means lessthan 1 weight percent (wt. %) of that component in a particular portionof a composition, such as a drilling fluid, sealing composition, lostcirculation material, spacer fluid, cleaning fluid, or other material.As an example, a lost circulation material that is substantially free ofsolids may have less than 1 wt. % solids based on the total weight ofthe lost circulation material.

As previously discussed in this disclosure, the sealing composition andLCM compositions of this disclosure may include an epoxy resin systemthat includes at least one epoxy resin and at least one curing agent.The epoxy resin may include bisphenol-A-based epoxy resins,bisphenol-F-based epoxy resins, aliphatic epoxy resins, Novalac resins,or combinations of these epoxy resins. Aliphatic epoxy resins may haveformula (I):

(OC₂H₃)—CH₂—O—R¹—O—CH₂—(C₂H₃O)  (I)

where R¹ may be a linear or branched hydrocarbyl having from 4 to 24carbon atoms, such as from 4 to 20, from 4 to 16, from 4 to 12, from 4to 8, from 6 to 24, from 6 to 20, from 6 to 16, or from 6 to 12 carbonatoms. In some embodiments, R¹ may be an alkyl group. For example, inone embodiment, the epoxy resin may include 1,6-hexanediol diglycidylether, which has formula (II):

(OC₂H₃)—CH₂—O—C₆H₁₂—O—CH₂—(C₂H₃O)  (II)

In some embodiments, the epoxy resin may include at least one of1,6-hexanediol diclycidyl ether, alkyl glycidyl ethers having from 12 to14 carbon atoms, 2,3-epoxypropyl o-tolyl ether, orbisphenol-A-epichlorohydrin epoxy resin. Alternatively, in otherembodiments, the epoxy resin may include at least one of 1,6-hexanedioldiclycidyl ether, alkyl glycidyl ethers having from 12 to 14 carbonatoms, or 2,3-epoxypropyl o-tolyl ether.

The epoxy resin may have an epoxy value of from 4.5 epoxy equivalentsper kilogram of the epoxy resin to 5.5 epoxy equivalents per kilogram ofthe epoxy resin. The epoxy equivalent weight of an epoxy resin is theweight of the epoxy resin in grams that contains one equivalent weightof epoxy. The epoxy equivalent weight of the epoxy resin is equal to themolecular weight of the epoxy resin divided by the average number ofepoxy groups in the epoxy resin. The epoxy resins may have an epoxyequivalent weight of from 170 to 350 grams of resin per epoxy equivalent(g/eq). The epoxy value and epoxy equivalent weight of an epoxy resinmay be determined according to ASTM-D1652. Other methods of determiningthe epoxy value and epoxy equivalent weight of the epoxy resin may alsobe used to determine the epoxy value or epoxy equivalent weight of theepoxy resin.

When used for a sealing composition, in some embodiments, the epoxyresin may have a viscosity that enables the sealing composition to betransferred into the annulus between the exterior surface of the tubularstring and the wellbore wall or the interior surface of a casingsurrounding the tubular string. In other embodiments, the epoxy resinmay have a viscosity that enables introduction of the sealingcomposition having the epoxy resin into a remediation area. When theepoxy resin system is included in the LCM composition, in someembodiments, the epoxy resin may have a viscosity that enables injectionof the LCM composition into a subterranean formation, such as alow-injectivity zone of a subterranean formation. In some embodiments,the epoxy resin may have a viscosity of from 200 millipascal seconds(mPa·s) to 50,000 mPa·s, from 200 mPa·s to 20,000 mPa·s, from 200 mPa·sto 15,000 mPa·s, from 200 mPa·s to 10,000 mPa·s, from 200 mPa·s to 5,000mPa·s, from 200 mPa·s to 2,000 mPa·s, from 500 mPa·s to 50,000 mPa·s,from 500 mPa·s to 20,000 mPa·s, from 500 mPa·s to 15,000 mPa·s, from 500mPa·s to 10,000 mPa·s, from 500 mPa·s to 5,000 mPa·s, from 500 mPa·s to2,000 mPa·s, from 1000 mPa·s to 50,000 mPa·s, from 1000 mPa·S to 20,000mPa·s, from 1000 mPa·s to 15,000 mPa·s, from 1000 mPa·s to 10,000 mPa·s,from 1000 mPa·s to 5,000 mPa·s, or from 1000 mPa·s to 2,000 mPa·s.

In some embodiments, the epoxy resin may be modified with a reactivediluent. The type and amount of reactive diluent may influence theviscosity, flexibility, hardness, chemical resistance, mechanicalproperties, plasticizing effect, reactivity, crosslinking density, orother properties of the epoxy resin. In some embodiments, the reactivediluent may be added to the epoxy resin to change the viscosity of theepoxy resin, such as to reduce the viscosity of the epoxy resin. Inother embodiments, the reactive diluents may be added to improve atleast one of the adhesion, the flexibility, and the solvent resistanceof the epoxy resin. The reactive diluent can be a non-functional,mono-functional, di-functional, or multi-functional reactive diluent.For example, a non-functional reactive diluent does not have an epoxidefunctional group. As used in relation to reactive diluents, the term“functional” refers to the reactive diluent having at least one epoxidefunctional group. Therefore, a functional reactive diluent may have one,two, three, or more than three epoxide functional groups. The term“non-functional”, as used in relation to reactive diluents, refers to areactive diluent that does not have at least one epoxide functionalgroup. Thus, a non-functional reactive diluent does not have at leastone epoxide functional group, but still participates in at least onechemical reaction during reaction of the epoxide resin. The term“non-reactive diluent” refers to a diluent that does not participate ina chemical reaction during reaction of the epoxy resin. Examples ofreactive and non-reactive diluents may include, but are not limited to,propylene glycol diglycidyl ether, butanediol diglycidyl ether, cardanolglycidyl ether derivatives, propanetriol triglycidyl ether, aliphaticmonoglycidyl ethers of C₁₃-C₁₅ alcohols, or combinations of functionalor non-functional reactive diluents and non-reactive diluents. In someembodiments, the epoxy resin may include a reactive diluent having theformula (III):

R²—O—CH₂—(C₂H₃O)  (III)

where R² is a hydrocarbyl having from 12 to 14 carbon atoms. R² may belinear, branched, or cyclic. In some embodiments, R² may be an alkylgroup.

In some embodiments, the epoxy resin may include an amount of reactivediluent that reduces the viscosity of the epoxy resin. In otherembodiments, the epoxy resin may include an amount of reactive diluentthat modifies one or more of the adhesion, the flexibility, or thesolvent resistance of the epoxy resin. In some embodiments, the epoxyresin may include from 1 wt. % to 30 wt. % reactive diluent based on thetotal weight of the epoxy resin portion of the epoxy resin system. Asused in this disclosure, the term “epoxy resin portion” refers to theconstituents of the epoxy resin system that do not include the curingagent, weighting agents, or other additives, such as accelerators orretarders. The epoxy resin portion includes the epoxy resins and anyadded reactive or non-reactive diluent. In other embodiments, the epoxyresin may include from 1 wt. % to 20 wt. %, from 1 wt. % to 16 wt. %,from 1 wt. % to 14 wt. %, from 1 wt. % to 12 wt. %, from 5 wt. % to 30wt. %, from 5 wt. % to 20 wt. %, from 5 wt. % to 16 wt. %, from 5 wt. %to 14 wt. %, from 5 wt. % to 12 wt. %, from 10 wt. % to 30 wt. %, from10 wt. % to 20 wt. %, from 10 wt. % to 16 wt. %, from 10 wt. % to 14 wt.%, from 12 wt. % to 30 wt. %, from 12 wt. % to 20 wt. %, from 12 wt. %to 16 wt. %, from 14 wt. % to 30 wt. %, from 14 wt. % to 20 wt. %, orfrom 14 wt. % to 16 wt. % reactive diluent based on the total weight ofthe epoxy resin portion of the epoxy system.

In some embodiments, the epoxy resin may includebisphenol-A-(epichlorohydrin) epoxy resin with oxirane mono[(C₁₂-C₁₄)-alkyloxy)methyl] derivatives. The bisphenol-A-epichlorohydrinepoxy resin is an epoxy resin made by reaction of bisphenol-A andepichlorohydrin. The bisphenol-A-(epichlorohydrin) epoxy resin may thenbe modified with the reactive diluent oxirane mono [(C₁₂-C₁₄)-alkyloxy)methyl] derivatives to reduce the viscosity of the resin and improve theadhesion, flexibility, and solvent resistance of the final resin. Thebisphenol-A-(epichlorohydrin) epoxy resin with the reactive diluentoxirane mono [(C₁₂-C₁₄)-alkyloxy) methyl] derivatives may modify theviscosity of the sealing compositions or LCM compositions, or mayprovide the sealing composition or the LCM composition with anon-crystalizing resin and improved mechanical and chemical resistancecompared to compositions without the bisphenol-A-(epichlorohydrin) epoxyresin with the reactive diluent oxirane mono [(C₁₂-C₁₄)-alkyloxy)methyl] derivatives. In some embodiments, the epoxy resin may includefrom 80 wt. % to 90 wt. %, from 80 wt. % to 88 wt. %, from 80 wt. % to86 wt. %, from 80 wt. % to 84 wt. %, from 82 wt. % to 90 wt. %, from 82wt. % to 88 wt. %, from 82 wt. % to 86 wt. %, from 82 wt. % to 84 wt. %,from 84 wt. % to 90 wt. %, from 84 wt. % to 88 wt. %, or from 84 wt. %to 86 wt. % of the bisphenyl-A-epichlorohydrin epoxy resin based on thetotal weight of the epoxy resin. In some embodiments, the epoxy resinmay include from 10 wt. % to 20 wt. %, from 10 wt. % to 18 wt. %, from10 wt. % to 16 wt. %, from 10 wt. % to 14 wt. %, from 12 wt. % to 20 wt.%, from 12 wt. % to 18 wt. %, from 12 wt. % to 16 wt. %, from 12 wt. %to 14 wt. %, from 14 wt. % to 20 wt. %, from 14 wt. % to 18 wt. %, orfrom 14 wt. % to 16 wt. % oxiranemono[(C₁₂-C₁₄)-alkyloxy)methyl]derivatives based on the total weight ofthe epoxy resin portion of the epoxy resin system.

In some embodiments, the epoxy resin comprising thebisphenol-A-(epichlorohydrin) epoxy resin with the reactive diluentoxirane mono [(C₁₂-C₁₄)-alkyloxy) methyl] derivatives may have an epoxyvalue of from 4.76 epoxy equivalents per kilogram of epoxy resin to 5.26epoxy equivalents per kilogram of epoxy resin. The epoxy resincomprising the bisphenol-A-(epichlorohydrin) epoxy resin with thereactive diluent oxirane mono [(C₁₂-C₁₄)-alkyloxy) methyl] derivativesmay have an epoxy equivalent weight of 190 g/eq to 210 g/eq and adynamic viscosity of from 600 millipascal seconds (mPa·s) to 1200 mPa·s,or 600 mPa·s to 900 mPa·s.

In some embodiments, the epoxy resin may include 2,3-epoxypropyl-o-tolylether, which may have an epoxy equivalent weight of from 170 g/eq to 190g/eq and exhibit a dynamic viscosity of from 7 mPa·s to 10 mPa·s. Inother embodiments, the epoxy resin may include alkyl glycidyl ethershaving from 12 to 14 carbon atoms, which may have an epoxy equivalentweight of from 270 g/eq to 305 g/eq and may exhibit a dynamic viscosityof from 5 mPa·s to 12 mPa·s. In some embodiments, the epoxy resin mayinclude 1,6-hexanediol diclycidyl ether, which may have an epoxyequivalent weight of from 150 g/eq to 170 g/eq and may exhibit a dynamicviscosity of from 20 mPa·s to 30 mPa·s.

In some embodiments, the epoxy resin system may include a plurality ofepoxy resins. For example, in some embodiments, the epoxy resin systemmay include a combination of two or more of bisphenol-A-epichlorohydrinepoxy resin, 2,3-epoxypropyl-o-tolyl ether, C₁₂-C₁₄ alkyl glycidylether, or 1,6-hexanediol diglycidyl ether epoxy resin. In oneembodiment, the epoxy resin may include a mixture of 1,6-hexanedioldiglycidyl ether epoxy resin and bisphenol-A-epichlorohydrin epoxy resinwith the reactive diluent oxirane mono[(C₁₂-C₁₄)-alkyloxy)methyl]derivatives.

In some embodiments, the sealing composition may include an amount ofthe epoxy resin necessary to form a cured epoxy composition. Forexample, in some embodiments, the sealing composition may include from20 wt. % to 99 wt. % epoxy resin based on the total weight of thesealing composition before curing. In other embodiments, the sealingcomposition may include from 20 wt. % to 97 wt. %, from 20 wt. % to 95wt. %, from 20 wt. % to 90 wt. %, from 20 wt. % to 80 wt. %, from 20 wt.% to 60 wt. %, from 40 wt. % to 99 wt. %, from 40 wt. % to 97 wt. %,from 40 wt. % to 95 wt. %, from 40 wt. % to 90 wt. %, from 40 wt. % to80 wt. %, from 40 wt. % to 60 wt. %, from 60 wt. % to 99 wt. %, from 60wt. % to 97 wt. %, from 60 wt. % to 95 wt. %, from 60 wt. % to 90 wt. %,from 60 wt. % to 80 wt. %, from 80 wt. % to 99 wt. %, from 80 wt. % to97 wt. %, from 80 wt. % to 95 wt. %, from 80 wt. % to 90 wt. %, from 90wt. % to 99 wt. %, from 90 wt. % to 97 wt. %, or from 90 wt. % to 95 wt.% epoxy resin based on the total weight of the sealing compositionbefore curing.

As previously discussed in this disclosure, the epoxy resin systemincludes a curing agent to cure the epoxy resin. The curing agent mayinclude at least one of an amine, polyamine, amine adduct, polyamineadduct, alkanolamine, amide, polyamide, polyamide adduct, polyamideimidazoline, polyaminoamides, phenalkamine, or combinations of these.Amines or polyamine curing agents may include, but are not limited to,aliphatic amines, cycloaliphatic amines, modified cycloaliphatic aminessuch as cycloaliphatic amines modified by polyacrylic acid, aliphaticpolyamines, cycloaliphatic polyamines, modified polyamines such aspolyamines modified by polyacrylic acid, or amine adducts such ascycloaliphatic amine adducts or polyamine adducts.

In some embodiments, the curing agent may include at least one oftrimethyl hexamethylene diamine (TMD), diethylenetriamine (DETA),triethylenetetramine (TETA), meta-xylenediamine (MXDA),aminoethylpiperazine (AEP), tetraethylenepentamine (TEPA),polyetheramine, isophoronediamine (IPDA), beta-hydroxyalkyl amide (HAA),or combinations of these. In other embodiments, the curing agent mayinclude at least one of DETA, TETA, TEPA, IPDA, or combinations ofthese. In some embodiments, the epoxy resin system may include aplurality of curing agents.

The curing agent may be an amine curing agent having an amine value thatenables the amine curing agent to fully cure the epoxy resin system. Theamine value of a curing agent gives the active hydrogen (NH) content ofan amine curing agent. The amine value is expressed as the weight inmilligrams of potassium hydroxide (KOH) needed to neutralize the NH in 1gram of the amine curing agent. In some embodiments, the curing agentmay have an amine value of from 250 milligrams of KOH per gram (mgKOH/g) to 1700 mg KOH/g, from 250 mg KOH/g to 1650 mg KOH/g, from 250 mgKOH/g to 1600 mg KOH/g, from 450 mg KOH/g to 1700 mg KOH/g, from 450 mgKOH/g to 1650 mg KOH/g, from 450 mg KOH/g to 1600 mg KOH/g, from 650 mgKOH/g to 1700 mg KOH/g, from 650 mg KOH/g to 1650 mg KOH/g, or from 650mg KOH/g to 1600 mg KOH/g. The amine value may be determined bytitrating a solution of the curing agent with a dilute acid, such as a 1N solution of hydrogen chloride (HCl). The amine value may then becalculated from the amount of HCl needed to neutralize the amine in thesolution according to Equation 1 (EQU. 1):

$\begin{matrix}\frac{V_{HCl}*N_{HCl}*{MW}_{KOH}}{W} & {{EQU}.\mspace{14mu} 1}\end{matrix}$

where V_(HC1) is the volume in milliliters of HCl needed to neutralizethe amine, N_(HC1) is the normality of HCl used to titrate the amine,MW_(KOH) is the molecular weight of KOH in grams per mole, and W is theweight in grams of the curing agent sample titrated. The amine number ofthe known pure amine curing agent may be calculated from Equation 2(EQU. 2):

$\begin{matrix}\frac{1000*{MW}_{KOH}}{{MW}_{{curing}\mspace{14mu} {agent}}} & {{EQU}.\mspace{14mu} 2}\end{matrix}$

where MW_(KOH) is the molecular weight of KOH in grams per mole, andMW_(curing agent) is the molecular weight of the curing agent in gramsper mole.

The amine curing agent may have an amine hydrogen equivalent weight(AHEW) that enables the amine curing agent to fully cure the epoxy resinsystem. The AHEW of an amine curing agent refers to the grams of theamine curing agent containing 1 equivalent of amine. The AHEW of anamine curing agent may be calculated by dividing the molecular weight ofthe amine curing agent in grams per mole by the number of activehydrogens per molecule. In some embodiments, the curing agent may be anamine curing agent having an AHEW of from 20 grams (g) to 120 g, from 20g to 115 g, from 20 g to 110 g, from 20 g to 100 g, from 40 g to 120 g,from 40 g to 115 g, from 40 g to 110 g, from 40 g to 110 g, from 60 g to120 g, from 60 g to 115 g, or from 60 g to 110 g determined according tothe methods previously described in this disclosure.

The curing time of the sealing composition may be inversely proportionalto the amount of curing agent in the sealing composition. For example,increasing the amount of the curing agent in the sealing composition mayresult in a decrease in the curing time of the sealing composition. Insome embodiments, the sealing composition may include an amount ofcuring agent capable of curing the epoxy resin in the sealingcomposition to a semi-solid state in a cure time of from 4 hours to 12hours. As used in this disclosure, the term “semi-solid” refers to astate of the compositions that is between a liquid and a solid in whichthe composition exhibits high elasticity and flexibility. In thesemi-solid state, the sealing composition may be easily deformed but mayreturn to shape upon releasing the deforming force. The sealingcompositions cured to a semi-solid or solid state are capable of sealingthe annulus of the wellbore.

In some embodiments, the sealing composition may include an amount ofthe curing agent capable of curing the epoxy resin system to asemi-solid state within a cure time of from 4 hours to 9 hours. In someembodiments, the sealing composition may include from 0.1 wt. % to 20wt. % curing agent based on the total weight of the sealing compositionbefore curing. In other embodiments, the sealing composition may havefrom 0.1 wt. % to 15 wt. %, from 0.1 wt. % to 10 wt. %, from 0.1 wt. %to 5 wt. %, from 0.5 wt. % to 20 wt. %, from 0.5 wt. % to 15 wt. %, from0.5 wt. % to 10 wt. %, from 0.5 wt. % to 5 wt. %, from 1 wt. % to 20 wt.%, from 1 wt. % to 15 wt. %, from 1 wt. % to 10 wt. %, from 1 wt. % to 5wt. %, from 5 wt. % to 20 wt. %, from 5 wt. % to 15 wt. %, from 5 wt. %to 10 wt. %, or from 10 wt. % to 20 wt. % curing agent based on thetotal weight of the sealing composition before curing.

The epoxy resin system may also include one or more additives to modifythe speed of the reaction between the epoxy resin and the curing agentor modify other properties of the resin system, such as viscosity, yieldpoint, or other rheological properties. For example, in someembodiments, the epoxy resin system may include an accelerator or aretarder to speed up or slow down the reaction between the epoxy resinand the curing agent. Accelerators may include, but are not limited to,alcohols, phenols, aminoalcohols, or amines. Examples of acceleratorsmay include, but are not limited to benzyl alcohol, mono-nonylphenol,triethanolamine (TEA), amino-n-propyl diethanolamine,n,n-dimethyldipropylenetramine, or combinations of these. Examples ofretarders may include lignin, gums, starches, lignosulphonatederivatives, or combinations of these.

In some embodiments, the sealing composition may include an amount ofthe accelerator capable of decreasing the cure time of the sealingcomposition from greater than 12 hours to a cure time in a range of from1 hour to 12 hours. In some embodiments, the sealing composition mayinclude from 0.01 wt. % to 10 wt. % accelerator based on the totalweight of the sealing composition prior to curing. In other embodiments,the sealing composition may include from 0.01 wt. % to 5 wt. %, from0.01 wt. % to 3 wt. %, from 0.01 wt. % to 1 wt. %, from 0.1 wt. % to 10wt. %, from 0.1 wt. % to 5 wt. %, from 0.1 wt. % to 3 wt. %, from 0.1wt. % to 1 wt. %, from 1 wt. % to 10 wt. %, from 1 wt. % to 5 wt. %, orfrom 1 wt. % to 3 wt. % accelerator based on the total weight of thesealing composition prior to curing.

The sealing compositions may include one or more weighting materials.The weighting materials may be particulate solids having a specificgravity (SG) that increases the density of the sealing composition. Theweighting material may be added to the sealing composition to increasethe density of the final cured resin to increase the hydrostaticpressure exerted by the sealing composition on the wellbore wall or theinterior surface of the outer tubular string. The final density of thecured resin may depend on the geology of the subterranean formation inthe zone being sealed. For example, in some embodiments, thesubterranean formation may require a sealing composition with a greaterdensity to support the wellbore and prevent flow of fluids from thesubterranean formation into the wellbore during curing of the sealingcomposition.

The weighting material may have a specific gravity (SG) of from 2 to 6.Examples of weighting materials may include, but are not limited to,sand, barite (barium sulfate), hematite, calcium carbonate, siderite,ilmenite, silica sand, manganese oxide (MnO), hausmanite (manganesetetraoxide (Mn₃O₄)), zin oxide, zirconium oxide, iron oxide, fly ash, orany combination of these weighting materials. In some embodiments,sealing composition may include manganese tetraoxide.

The sealing composition may include an amount of weighting material thatincreases the density of the sealing composition. In some embodiments,the sealing composition may include from 0.1 wt. % to 40 wt. % weightingmaterial based on the total weight of the sealing composition prior tocuring. For example, in some embodiments, the sealing composition mayinclude from 0.1 wt. % to 30 wt. %, from 0.1 wt. % to 20 wt. %, from 0.1wt. % to 10 wt. %, from 1 wt. % to 40 wt. %, from 1 wt. % to 30 wt. %,from 1 wt. % to 20 wt. %, from 1 wt. % to 10 wt. %, from 5 wt. % to 40wt. %, from 5 wt. % to 30 wt. %, from 5 wt. % to 20 wt. %, from 5 wt. %to 10 wt. %, from 10 wt. % to 40 wt. %, from 10 wt. % to 30 wt. %, from10 wt. % to 20 wt. %, or from 20 wt. % to 40 wt. % weighting materialbased on the total weight of the sealing composition before curing.

In some embodiments, the epoxy resin system may include other modifiers,such as cardanol liquid, polyacrylate flow agents, or combinations ofthese. Modifiers may be added to the epoxy resin system to decrease theviscosity of the epoxy resin.

In some embodiments, the sealing composition may include from 20 wt. %to 97 wt. % epoxy resin based on the total weight of the composition,where the epoxy resin comprises at least one of 2,3-epoxypropyl o-tolylether, alkyl glycidyl ethers having from 12 to 14 carbon atoms, or thecompound having formula (I):

(OC₂H₃)—CH₂—O—R¹—O—CH₂—(C₂H₃O)  (I)

where R¹ is a linear or branched hydrocarbyl having from 4 to 24 carbonatoms, and from 1 weight percent to 20 weight percent curing agent basedon the total weight of the composition. Alternatively, in otherembodiments, the sealing composition may include from 20 wt. % to 97 wt.% bisphenol-A-epichlorohydrin epoxy resin with the reactive diluentoxirane mono [(C₁₂-C₁₄)-alkyloxy)methyl] derivatives and 1 wt. % to 20wt. % TEPA curing agent. In other embodiments, the sealing compositionmay include 10 wt. % to 80 wt. % bisphenol-A-epichlorohydrin epoxy resinwith the reactive diluent oxirane mono [(C₁₂-C₁₄)-alkyloxy)methyl]derivatives, 10 wt. % to 80 wt. % 1,6-hexanediol diglycidyl ether, 1 wt.% to 20 wt. % TEPA. In some embodiments, the sealing composition mayinclude from 1 wt. % to 40 wt. % Mn₃O₄ weighting material.

The epoxy resins in the epoxy resin system are initially in liquid form.Upon combining the epoxy resins with the curing agents, the epoxy resinsreact with the curing agents to transform into a semi-solid or solidepoxy resin. Transition of epoxy resin from a liquid to a solid involvesformation of covalent bonds via cross-linking reactions that initiallybuild viscosity in the sealing compositions. Thus, during the curingprocess in which the epoxy resins transform from liquid to solid throughcross-linking, the buildup of viscosity in the sealing compositions mayenable the sealing compositions to continue to transmit hydrostaticpressure to the hydrocarbon-bearing formation. At a cross-over point inthe curing process, the epoxy resins may begin to form into a non-porousthree-dimensional network. As this non-porous three-dimensional networkbegins to form, the epoxy resin continues to transmit hydrostaticpressure to the formation until an impermeable barrier of cured epoxyresin forms.

The sealing composition may have a cure time that enables the sealingcomposition to be transferred into the wellbore annulus, casing-casingannulus, remediation zone, or other region of the wellbore before thebuildup of viscosity causes transfer problems, such as inability to pumpthe sealing composition. In some embodiments, the sealing compositionmay have a cure time of greater than or equal to 4 hours, greater thanor equal to 5 hours, or greater than or equal to 6 hours. In someembodiments, the sealing composition may have a cure time of less thanor equal to 12 hours, less than or equal to 10 hours, or even less thanor equal to 9 hours. In some embodiments, the sealing composition mayhave a cure time of from 4 hours to 12 hours, from 4 hours to 10 hours,from 4 hours to 9 hours, from 4 hours to 6 hours, from 5 hours to 12hours, from 5 hours to 10 hours, from 5 hours to 9 hours, from 6 hoursto 12 hours, from 6 hours to 10 hours, from 6 hours to 9 hours, from 9hours to 12 hours, or from 10 hours to 12 hours.

The sealing compositions can be used for sealing the annulus orremediating a wellbore under a range of different downhole conditions inthe wellbore. For example, in some embodiments, the sealing compositionmay be adapted to different downhole conditions by changing theconcentrations of the epoxy resin, curing agents, accelerators, orweighting materials in the sealing composition to modify the specificgravity, viscosity, mechanical properties, curing time, or otherproperties of the sealing compositions.

The sealing compositions may be capable of withstanding a wide range oftemperatures and pressures without failing or deteriorating. Failure ordeterioration of the sealing composition may allow liquids or gases topenetrate into or through the sealing composition. For example, thesealing compositions, once cured, may be capable of withstandingtemperatures of from 20 degrees Celsius (° C.) to 205° C. The curedsealing compositions may also be able to withstand temperature cyclingwithin a temperature range of from 20° C. to 205° C. The cured sealingcomposition may be capable of withstanding pressures of up to 4,000,000pounds of force per square inch (psi) (1 psi equals 6.89476 kilopascals(kPa)). For example, in some embodiments, the cured sealing compositionmay be capable of withstanding pressures of from 14 psi to 4,000,000 psiwithout failing or deteriorating to allow liquids or gases to penetrateinto or through the sealing composition.

The rheology and density of the sealing compositions can be adjustedover a wide range of values depending on the requirement for the welland the downhole conditions of the well. The sealing composition mayhave a density that enables the sealing composition to exert hydrostaticpressure on the wellbore wall or interior surface of an outer casing tosupport the wellbore, prevent fluids from flowing from the subterraneanformation into the wellbore, or both. In some embodiments, the sealingcomposition may have a density of from 55 pounds per cubic foot(lbm/ft³) to 170 lbm/ft³ measured immediately after addition of thecuring agent and before substantial curing has occurred. As used in thisdisclosure, the term “substantial curing” refers to an amount of curingthat produces a change of greater than 5 percent (%) in any rheologicalproperty of the composition. In some embodiments, the sealingcomposition may have a density of from 55 lbm/ft³ to 150 lbm/ft³, from55 lbm/ft³ to 130 lbm/ft³, from 55 lbm/ft³ to 110 lbm/ft³, from 55lbm/ft³ to 90 lbm/ft³, from 60 lbm/ft³ to 170 lbm/ft³, from 60 lbm/ft³to 150 lbm/ft³, from 60 lbm/ft³ to 130 lbm/ft³, from 60 lbm/ft³ to 110lbm/ft³, from 60 lbm/ft³ to 90 lbm/ft³, from 80 lbm/ft³ to 170 lbm/ft³,from 80 lbm/ft³ to 130 lbm/ft³, from 80 lbm/ft³ to 110 lbm/ft³, from 90lbm/ft³ to 150 lbm/ft³, or from 90 lbm/ft³ to 130 lbm/ft³. In someembodiments, the sealing composition may have a density of from 55pounds per cubic foot (lbm/ft³) to 170 lbm/ft³ measured immediatelyafter addition of the curing agent and before substantial curing hasoccurred.

For primary sealing and remedial sealing operations, the sealingcomposition may be formulated to have reduced resistance to flowcompared to LCM compositions. The reduced resistance to flow of thesealing composition may enable the sealing composition to be easilytransferred into the annulus. In some embodiments, the sealingcomposition may have a viscosity that enables the sealing composition toexert hydrostatic pressure on the wellbore wall or interior surface ofan outer casing to support the wellbore, prevent fluids from flowingfrom the subterranean formation into the wellbore, or both. However, theviscosity of the sealing composition may be reduced to enable thesealing composition to be efficiently transported into the annulus. Insome embodiments, the sealing composition may have a viscosity of from 1millipascal second (mPa·s) to 50,000 mPa·s before curing. The viscosityof the sealing composition may be determined according to the methodssubsequently provided in this disclosure. In some embodiments, thesealing composition may have a viscosity of from 1 mPa·s to 100,000mPa·s, from 1 mPa·s to 10,000 mPa·s, from 1 mPa·s to 1,000 mPa·s, from 1mPa· to 500 mPa·s, from 1 mPa·s to 100 mPa·s, from 1 mPa·s to 10 mPa·s,from 2 mPa·s to 200,000 mPa·s, from 2 mPa·s to 100,000 mPa·s, from 2mPa·s to 10,000 mPa·s, from 2 mPa·s to 1,000 mPa·s, from 2 mPa· to 500mPa·s, from 2 mPa·s to 100 mPa·s, from 2 mPa·s to 10 mPa·s, from 10mPa·s to 200,000 mPa·s, from 10 mPa·s to 100,000 mPa·s, from 10 mPa· to10,000 mPa·s, from 100 mPa·s to 200,000 mPa·s, from 100 mPa·s to 100,000mPa·s, from 100 mPa·s to 10,000 mPa·s, from 100 mPa·s to 1,000 mPa·s,from 1,000 mPa· to 200,000 mPa·s, from 1,000 mPa·s to 100,000 mPa·s,from 1,000 mPa·s to 10,000 mPa·s, from 10,000 mPa·s to 200,000 mPa·s, orfrom 10,000 mPa·s to 100,000 mPa·s measured immediately after additionof the curing agent and before substantial curing has taken place.

The sealing composition may have a gel strength before curing thatmaintains the pump-ability of the sealing composition to preventstuck-pipe problems. The gel strength refers to the shear stress of afluid measured at a reduced shear rate following a defined period oftime during which the fluid is maintained in a static state. In someembodiments, the sealing composition may have a density of greater than100 lbm/ft³ or greater than 120 lbm/ft³, and the gel strength may enablethe sealing composition to suspend the weighting agents in sealingcomposition added to increase the density. In some embodiments, thesealing compositions may have a 10-second gel strength of from 0.1 poundof force per square foot (lbf/100 ft²) to 20 lbf/100 ft², from 0.1lbf/100 ft² to 10 lbf/100 ft², from 0.1 lbf/100 ft² to 5 lbf/100 ft²,from 1 lbf/100 ft² to 20 lbf/100 ft², from 1 lbf/100 ft² to 10 lbf/100ft², from 1 lbf/100 ft² to 5 lbf/100 ft², from 5 lbf/100 ft² to 20lbf/100 ft², from 5 lbf/100 ft² to 10 lbf/100 ft², or from 0.1 lbf/100ft² to 1 lbf/100 ft² measured immediately after addition of the curingagent and before substantial curing has taken place. In someembodiments, the sealing composition may have a 10-minute gel strengthof from 0.1 lbf/100 ft² to 30 lbf/100 ft², from 0.1 lbf/100 ft² to 20lbf/100 ft², from 0.1 lbf/100 ft² to 10 lbf/100 ft², from 0.1 lbf/100ft² to 5 lbf/100 ft², from 1 lbf/100 ft² to 30 lbf/100 ft², from 1lbf/100 ft² to 20 lbf/100 ft², from 1 lbf/100 ft² to 10 lbf/100 ft²,from 1 lbf/100 ft² to 5 lbf/100 ft², from 5 lbf/100 ft² to 30 lbf/100ft², from 5 lbf/100 ft² to 2 lbf/100 ft², from 5 lbf/100 ft² to 10lbf/100 ft², from 10 lbf/100 ft² to 30 lbf/100 ft², from 10 lbf/100 ft²to 20 lbf/100 ft², or from 20 lbf/100 ft² to 30 lbf/100 ft² measuredimmediately after addition of the curing agent and before substantialcuring has taken place. The 10-second gel strength and 10-minute gelstrength may be measured according to the test methods subsequentlydescribed in this disclosure.

The plastic viscosity (PV) of a fluid relates to the resistance of afluid to flow due to mechanical interaction between the solids of thefluid and represents the viscosity of the fluid extrapolated to infiniteshear rate. The sealing composition may have a PV that enables thesealing composition to be easily transferred through the interior volumeof the tubular string and into the annulus. The PV of the sealingcomposition may be measured immediately after addition of the curingagent and before substantial curing has taken place. The PV of thesealing composition may be determined in accordance with the testmethods subsequently described in this disclosure. In some embodiments,the sealing composition may have a PV of from 0.1 centipoise (cP) to 50cP, from 0.1 cP to 30 cP, from 0.1 cP to 20 cP, from 0.1 cP to 10 cP,from 1 cP to 50 cP, from 1 cP to 30 cP, from 1 cP to 20 cP, from 1 cP to10 cP, from 5 cP to 50 cP, from 5 cP to 30 cP, from 5 cP to 20 cP, orfrom 5 cP to 10 cP measured immediately after addition of the curingagent and before substantial curing has taken place (1 cP=1 millipascalsecond (mPa·s)). The PV of the sealing composition may depend on thequantity of solids added to the sealing composition. For example,addition of weighting agents to the sealing composition to increase thedensity may also increase the PV of the sealing composition.

The yield point (YP) of a fluid relates to the amount of stress requiredto move the fluid from a static condition. In some embodiments, thesealing compositions may have a YP that enables the sealing compositionto be efficiently transferred into the annulus. Alternatively, in otherembodiments, the sealing compositions may include weighting agents andmay have a greater YP to enable the sealing compositions to suspend theweighting agents. In some embodiments, the sealing composition may havea YP that prevents the sealing composition from flowing out ofremediation zone when the sealing composition is used in remedialoperations to repair the well. In some embodiments, the sealingcomposition may have a YP of from 0.1 lbf/100 ft² to 400 lbf/100 ft²,from 0.1 lbf/100 ft² to 300 lbf/100 ft², from 0.1 lbf/100 ft² to 200lbf/100 ft², from 0.1 lbf/100 ft² to 100 lbf/100 ft², from 0.1 lbf/100ft² to 10 lbf/100 ft², from 1 lbf/100 ft² to 400 lbf/100 ft², from 1lbf/100 ft² to 300 lbf/100 ft², from 1 lbf/100 ft² to 200 lbf/100 ft²,from 1 lbf/100 ft² to 100 lbf/100 ft², from 1 lbf/100 ft² to 10 lbf/100ft², from 10 lbf/100 ft² to 400 lbf/100 ft², from 10 lbf/100 ft² to 300lbf/100 ft², from 10 lbf/100 ft² to 200 lbf/100 ft², from 10 lbf/100 ft²to 100 lbf/100 ft², from 100 lbf/100 ft² to 400 lbf/100 ft², from 100lbf/100 ft² to 300 lbf/100 ft², from 100 lbf/100 ft² to 200 lbf/100 ft²,from 200 lbf/100 ft² to 400 lbf/100 ft², or from 300 lbf/100 ft² to 400lbf/100 ft².

The epoxy resins, once cured, may be more chemically resistant thanconventional cement compositions. For example, the fluids from thesubterranean formation, such as hydrocarbon gases, crude oil, orproduced water, may include hydrogen sulfide gas (H₂S), which is highlycorrosive. In some embodiments, the cured epoxy resins incorporated intothe sealing compositions and LCM compositions may be resistant tocorrosion caused by H₂S gas present in fluids in the subterraneanformation.

In some embodiments, the sealing composition may include a cement slurryin addition to the epoxy resin and the curing agent. For example, insome embodiments, the sealing composition may include from 0.1 wt. % to75 wt. % cement slurry based on the total weight of the sealingcomposition. In other embodiments, the sealing composition may includefrom 0.1 wt. % to 50 wt. %, from 0.1 wt. % to 25 wt. %, from 0.1 wt. %to 10 wt. %, from 1 wt. % to 75 wt. %, from 1 wt. % to 50 wt. %, from 1wt. % to 25 wt. %, from 1 wt. % to 10 wt. %, from 10 wt. % to 75 wt. %,from 10 wt. % to 50 wt. %, from 10 wt. % to 25 wt. %, from 25 wt. % to75 wt. %, from 25 wt. % to 50 wt. %, or from 50 wt. % to 75 wt. % cementslurry based on the total weight of the sealing composition.

The cement slurry may include water, a cement precursor material, and asurfactant. The cement precursor material may be any suitable materialwhich, when mixed with water, can be cured into a cement. The cementprecursor material may be hydraulic or non-hydraulic cement precursors.A hydraulic cement precursor material refers to a mixture of limestone,clay and gypsum burned together under extreme temperatures that maybegin to harden instantly or within a few minutes while in contact withwater. A non-hydraulic cement precursor material refers to a mixture oflime, gypsum, plasters and oxychloride. A non-hydraulic cement precursormay take longer to harden or may require drying conditions for properstrengthening, but often is more economically feasible. While hydrauliccement may be more commonly utilized in drilling applications, it shouldbe understood that other cements are contemplated. In some embodiments,the cement precursor material may be Portland cement precursor. Portlandcement precursor is a hydraulic cement precursor (cement precursormaterial that not only hardens by reacting with water but also forms awater-resistant product) produced by pulverizing clinkers, which containhydraulic calcium silicates and one or more of the forms of calciumsulphate as an inter-ground addition.

The cement precursor material may include one or more of calciumhydroxide, silicates, oxides, belite (Ca₂SiO₅), alite (Ca₃SiO₄),tricalcium aluminate (Ca₃Al₂O₆), tetracalcium aluminoferrite(Ca₄Al₂Fe₂O₁₀), brownmilleriate (4CaO.Al₂O₃.Fe₂O₃), gypsum (CaSO₄.2H₂O)sodium oxide, potassium oxide, limestone, lime (calcium oxide),hexavalent chromium, calcium alluminate, or combinations of these. Thecement precursor material may include Portland cement, siliceous flyash, calcareous fly ash, slag cement, silica fume, any known cementprecursor material or combinations of any of these. In some embodiments,the cement slurry may contain from 10 wt. % to 90 wt. % of the cementprecursor material based on the total weight of the cement slurry. Forinstance, the cement slurry may contain from 10 wt. % to 80 wt. %, from10 wt. % to 70 wt. %, from 10 wt. % to 60 wt. %, or from 10 wt. % to 50wt. % of the cement precursor material.

Water may be added to the cement precursor material to produce thecement slurry. The water may be distilled water, deionized water, or tapwater. In some embodiments, the water may contain additives orcontaminants. For instance, the water may include freshwater orseawater, natural or synthetic brine, salt water, formation water, orbrackish water, or combinations of these. In some embodiments, salt orother organic compounds may be incorporated into the water to controlcertain properties of the water, and thus the cement slurry, such asdensity. Suitable salts may include, but are not limited to, alkalimetal chlorides, hydroxides, or carboxylates. In some embodiments,suitable salts may include sodium, calcium, cesium, zinc, aluminum,magnesium, potassium, strontium, silicon, lithium, chlorides, bromides,carbonates, iodides, chlorates, bromates, formates, nitrates, sulfates,phosphates, oxides, fluorides, and combinations of these. In someembodiments, the cement slurry may contain from 5 wt. % to 70 wt. %water based on the total weight of the cement slurry.

The cement slurry may contain from 0.1 wt. % to 10 wt. % of thesurfactant based on the total weight of the cement slurry. In someembodiments, the cement slurry may contain from 0.1 wt. % to 50 wt. % ofthe one or more additives based on the total weight of the cementslurry. In some embodiments, the one or more additives may include adispersant containing one or more anionic groups. For instance, thedispersant may include synthetic sulfonated polymers, lignosulfonateswith carboxylate groups, organic acids, hydroxylated sugars, otheranionic groups, or combinations of any of these. In some embodiments,the one or more additives may alternatively or additionally include afluid loss additive. In some embodiments, the cement fluid loss additivemay include non-ionic cellulose derivatives. In some embodiments, thecement fluid loss additive may be hydroxyethylcellulose (HEC). In otherembodiments, the fluid loss additive may be a non-ionic syntheticpolymer (for example, polyvinyl alcohol or polyethyleneimine). In someembodiments, the fluid loss additive may be an anionic syntheticpolymer, such as 2-acrylamido-2-methylpropane sulfonic acid (AMPS) orAMPS-copolymers, including lattices of AMPS-copolymers. In someembodiments, the fluid loss additive may include bentonite, which mayadditionally viscosify the cement slurry and may, in some embodiments,cause retardation effects.

The sealing compositions described in this disclosure may be used inmethods for primary sealing an annulus of a wellbore or in methods ofremediating or repairing weak zones of a cement sheath of an existinghydrocarbon production well. Weak zones may be identified from a welllog generated from physical measurement of the wellbore by one or aplurality of instruments inserted into the wellbore. In someembodiments, a method for sealing an annulus of a wellbore may includeintroducing a spacer fluid into a tubular string positioned in thewellbore, the spacer fluid displacing at least a portion of a drillingfluid disposed in the wellbore. The method may also include introducinga sealing composition into the tubular string positioned in the wellboreto displace at least a portion of the spacer fluid. The sealingcomposition may include any of the sealing compositions previouslydescribed in this disclosure. The method may further include introducinga displacement fluid into the wellbore to transfer the sealingcomposition into an annulus of the well and curing the sealingcomposition.

In some embodiments, the method may further include curing the sealingcomposition for at least 4 hours. Alternatively, in other embodiments,the method may include curing the sealing composition for a cure time offrom 4 hours to 12 hours. In some embodiments, the spacer fluid and thesealing composition may be introduced to the wellbore through the drillstring.

In other embodiments, a method for repairing a weak zone in ahydrocarbon production well may include perforating at least one tubularstring in the weak zone of the hydrocarbon production well and injectingthe sealing composition through the tubular string and into the weakzone of the hydrocarbon production well. The sealing composition mayinclude any of the sealing compositions previously described in thisdisclosure. The method may further include curing the sealingcomposition.

In some embodiments, the method may further include identifying the weakzone of a cement sheath of the hydrocarbon production well. In someembodiments, the weak zones of a cement sheath may be identified byexamining the cement bond log. The cement bond log refers todocumentation of the integrity of the cement seal placed in the wellboreannulus or casing-casing annulus of the wellbore and may be generatedusing a sonic resonance tool or other tool to evaluate the bonding ofthe cement composition in the annuli. Additionally, in some embodiments,the method may include determining the volume and densities of thespacer fluid, preflush fluid, or both. The method may further includedetermining the density, volume, or both of the sealing composition tobe injected into the weak zones.

LCM compositions that include the epoxy resin system will now bedescribed. As previously discussed in this disclosure, the LCMcompositions may include the epoxy resin system comprising at least oneepoxy resin and at least one curing agent. The LCM compositions mayinclude any of the epoxy resins, reactive or non-reactive diluents, orcuring agents previously described in this disclosure.

In some embodiments, the LCM composition may include an amount of theepoxy resin necessary to form a cured epoxy composition. For example, insome embodiments, the LCM composition may include from 50 wt. % to 97wt. % epoxy resin based on the total weight of the LCM compositionbefore curing. In other embodiments, the LCM composition may includefrom 50 wt. % to 95 wt. %, from 50 wt. % to 90 wt. %, from 50 wt. % to80 wt. %, from 50 wt. % to 70 wt. %, from 50 wt. % to 60 wt. %, from 60wt. % to 97 wt. %, from 60 wt. % to 95 wt. %, from 60 wt. % to 90 wt. %,from 60 wt. % to 80 wt. %, from 60 wt. % to 70 wt. %, from 70 wt. % to97 wt. %, from 70 wt. % to 95 wt. %, from 70 wt. % to 90 wt. %, from 70wt. % to 80 wt. %, from 80 wt. % to 97 wt. %, from 80 wt. % to 95 wt. %,from 80 wt. % to 90 wt. %, from 90 wt. % to 97 wt. %, from 90 wt. % to95 wt. %, or from 95 wt. % to 97 wt. % epoxy resin based on the totalweight of the LCM composition before curing.

In some embodiments, the LCM composition for sealing lost circulationzones may include an amount of curing agent that cures the epoxy resinin less than 3 hours, less than 2 hours, or even less than 1 hour. Insome embodiments, the LCM composition may include an amount of curingagent that cures the epoxy resin within a curing time of from 0.5 hoursto 3 hours. In some embodiments, the LCM composition may include from 2wt. % to 30 wt. % curing agent based on the total weight of the LCMcomposition before curing. In other embodiments, the LCM composition mayhave from 2 wt. % to 25 wt. %, from 2 wt. % to 20 wt. %, from 2 wt. % to15 wt. %, from 2 wt. % to 10 wt. %, from 5 wt. % to 30 wt. %, from 5 wt.% to 25 wt. %, from 5 wt. % to 20 wt. %, from 5 wt. % to 15 wt. %, from5 wt. % to 10 wt. %, from 10 wt. % to 30 wt. %, from 10 wt. % to 25 wt.%, from 10 wt. % to 15 wt. %, or from 10 wt. % to 20 wt. % curing agentbased on the total weight of the LCM composition before curing.

Additionally, the LCM compositions may include any of the weightingagents, accelerators, or retarders previously described in thisdisclosure. For example, in some embodiments, the LCM composition mayinclude an accelerator. In some embodiments, the LCM composition mayinclude an amount of the accelerator that decreases the cure time from 4hours or more to less than 3 hours so that the cure time may be in arange of from 0.5 hours to 3 hours. In some embodiments, the LCMcomposition may include from 0.01 wt. % to 10 wt. % accelerator based onthe total weight of the LCM composition prior to curing. In otherembodiments, the LCM composition may include from 0.01 wt. % to 5 wt. %,from 0.01 wt. % to 3 wt. %, from 0.01 wt. % to 1 wt. %, from 0.1 wt. %to 10 wt. %, from 0.1 wt. % to 5 wt. %, from 0.1 wt. % to 3 wt. %, from0.1 wt. % to 1 wt. %, from 1 wt. % to 10 wt. %, from 1 wt. % to 5 wt. %,or from 1 wt. % to 3 wt. % accelerator based on the total weight of theLCM composition prior to curing.

The LCM compositions may include one or more weighting materials. Theweighting materials may be particulate solids having a specific gravity(SG) that increases the density of the LCM composition. Weightingmaterials may be added to the LCM compositions to increase the densityof the final cured epoxy resin and to increase the hydrostatic pressureexerted by the LCM composition on the formation into which the LCMcomposition is introduced. As previously discussed in this disclosure,the final density of the cured resin of the LCM composition may dependon the geology of the subterranean formation in the zone beingremediated. For example, in some embodiments, the subterranean formationmay require a LCM composition with a greater density to support thewellbore and prevent flow of fluids from the subterranean formation intothe wellbore during curing of the sealing composition. The increaseddensity and hydrostatic pressure of the LCM composition may preventdisplacement of the LCM composition by fluids from the formation.

The LCM composition may include an amount of weighting material thatincreases the density of the LCM composition. The weighting materialadded to the LCM may be any of the weighting materials previouslydescribed in this disclosure. In some embodiments, the LCM compositionmay include from 0.1 wt. % to 40 wt. % weighting material based on thetotal weight of the LCM composition prior to curing. For example, insome embodiments, the LCM composition may include from 0.1 wt. % to 30wt. %, from 0.1 wt. % to 20 wt. %, from 0.1 wt. % to 10 wt. %, from 1wt. % to 40 wt. %, from 1 wt. % to 30 wt. %, from 1 wt. % to 20 wt. %,from 1 wt. % to 10 wt. %, from 5 wt. % to 40 wt. %, from 5 wt. % to 30wt. %, from 5 wt. % to 20 wt. %, from 5 wt. % to 10 wt. %, from 10 wt. %to 40 wt. %, from 10 wt. % to 30 wt. %, from 10 wt. % to 20 wt. %, orfrom 20 wt. % to 40 wt. % weighting material based on the total weightof the LCM composition before curing.

The epoxy resins in the LCM composition are initially in liquid form. Aspreviously described in this disclosure, the epoxy resins buildviscosity during curing and eventually cure to a non-porousthree-dimensional network. The LCM compositions may have a cure timethat is less than the cure time of the sealing compositions. In someembodiments, the LCM compositions may have a cure time of less than orequal to 3 hours, less than or equal to 2 hours, or less than or equalto 1 hour. In other embodiments, the LCM compositions may have a curetime of from 0.1 hours to 3 hours, from 0.1 hours to 2 hours, from 0.1hour to 1 hours, from 0.1 hours to 0.5 hour, 0.5 hours to 3 hours, from0.5 hours to 2 hours, from 0.5 hour to 1 hours, 1 hour to 3 hours, from1 hour to 2 hours, or from 2 hour to 3 hours.

As previously described, the LCM composition may include 50 wt. % to 97wt. % epoxy resin and from 2 wt. % to 30 wt. % curing agent. In someembodiments, the curing agent may include at least one of TEPA, DETA,TETA, or IPDA. In some embodiments, the epoxy resin of the LCMcomposition may include from 0.1 weight percent to 80 weight percentbisphenol-A-epichlorohydrin epoxy resin based on the total weight of theepoxy resin in the composition and further comprises a reactive diluent.The reactive diluent may comprise the balance of the epoxy resin of theLCM composition. In some embodiments, the reactive diluent may includeR²—O—CH₂—(C₂H₃O), where R² is an alkyl having from 12 to 14 carbonatoms. In some embodiments, the LCM composition may comprise, consistof, or consist essentially of 50 wt. % to 80 wt. %bisphenol-A-epichlorohydrin epoxy resin based on the total weight of theepoxy resin in the composition, 14 wt. % to 16 wt. % reactive diluent,and 1 wt. % to 30 wt. % TEPA curing agent. In other embodiments, the LCMcomposition may include from 50 wt. % to 97 wt. % epoxy resin comprisinga combination of 1,6-hexanediol diclycidyl ether andbisphenol-A-epichlorohydrin epoxy resin.

The LCM compositions may be used for sealing lost circulation zones in awellbore under a range of different downhole conditions. For example, insome embodiments, the LCM composition may be adapted to differentdownhole conditions by changing the concentrations of the epoxy resin,curing agents, accelerators, or weighting materials in the LCMcompositions to modify the specific gravity, viscosity, mechanicalproperties, curing time, or other properties of the LCM compositions.

The LCM compositions may be capable of withstanding a wide range oftemperatures and pressures without failing or deteriorating to allowliquids or gases to penetrate into or through the LCM compositions. Forexample, the LCM compositions, once cured, may be capable ofwithstanding temperatures of from 20 degrees Celsius (° C.) to 205° C.The cured LCM compositions may also be able to withstand temperaturecycling within a temperature range of from 20° C. to 205° C. The curedLCM compositions may be capable of withstanding pressures of up to4,000,000 pounds of force per square inch (psi) (1 psi equals 6.89476kilopascals (kPa)). For example, in some embodiments, the cured LCMcompositions may be capable of withstanding pressures of from 14 psi to4,000,000 psi without failing or deteriorating to allow liquids or gasesto penetrate into or through the LCM compositions.

The rheology and density of the LCM compositions can be adjusted over awide range of values depending on the requirement for the well and thedownhole conditions of the well. The LCM composition may have a densitythat enables the LCM composition to exert hydrostatic pressure on theformation when introduced to the lost circulation zone. In someembodiments, the LCM composition may have a density as previouslydescribed in this disclosure for the sealing composition.

For remediation of lost circulation zones, the LCM compositions may beformulated to have greater resistance to flow (greater rheology)compared to sealing compositions. The greater resistance to flow of theLCM composition may enable the LCM composition to be introduced to thelost circulation zone while preventing the LCM composition from flowingeasily through the lost circulation zone and being lost to theformation. In some embodiments, the LCM composition may have a viscositythat enables the LCM composition to exert hydrostatic pressure withinthe formation to prevent loss of the LCM composition to the formation.However, the viscosity of the LCM composition may enable the LCMcomposition to be efficiently injected into the formation in the lostcirculation zone. In some embodiments, the LCM composition may have aviscosity of from 2 millipascal second (mPa·s) to 200,000 mPa·s beforecuring. The viscosity of the LCM compositions may be determinedaccording to the methods subsequently provided in this disclosure. Insome embodiments, the LCM composition may have a viscosity of from 2mPa·s to 100,000 mPa·s, from 2 mPa·s to 10,000 mPa·s, from 2 mPa·s to1,000 mPa·s, from 2 mPa· to 500 mPa·s, from 2 mPa·s to 100 mPa·s, from 2mPa·s to 10 mPa·s, from 10 mPa·s to 200,000 mPa·s, from 10 mPa·s to100,000 mPa·s, from 10 mPa· to 10,000 mPa·s, from 100 mPa·s to 200,000mPa·s, from 100 mPa·s to 100,000 mPa·s, from 100 mPa·s to 10,000 mPa·s,from 100 mPa·s to 1,000 mPa·s, from 1,000 mPa· to 200,000 mPa·s, from1,000 mPa·s to 100,000 mPa·s, from 1,000 mPa·s to 10,000 mPa·s, from10,000 mPa·s to 200,000 mPa·s, or from 10,000 mPa·s to 100,000 mPa·sbefore curing.

The LCM composition may have a gel strength before curing that maintainsthe pump-ability of the LCM composition to prevent stuck-pipe problems.In some embodiments, the LCM composition may have a density of greaterthan 100 lbm/ft³ or greater than 120 lbm/ft³, and may have a gelstrength that enables the LCM composition to suspend the weightingagents added to increase the density. In some embodiments, the LCMcomposition may have a gel strength before curing that prevents the LCMcomposition from flowing further into the formation after injection ofthe LCM into the formation. In some embodiments, the LCM composition mayhave a 10-second gel strength and a 10-minute gel strength as previouslydescribed in this disclosure for the sealing composition.

The LCM composition may have a PV that enables the LCM composition to beinjected into the formation, such as into a low-injectivity zone. Insome embodiments, the LCM composition may have a PV as previouslydescribed in this disclosure for the sealing composition.

In some embodiments, the LCM compositions may have a YP that preventsthe LCM composition from flowing further into the formation once the LCMcomposition has been introduced to the formation, such as throughinjection. In some embodiments, the LCM composition may includeweighting agents and may have a YP that enables the LCM composition tosuspend the weighting agent in the LCM composition and reduce settling.In some embodiments, the LCM composition may have a YP as previouslydescribed in this disclosure for the sealing composition.

The LCM compositions may be used in a method to isolate a lostcirculation zone of a wellbore, which may be encountered during drillingoperations. The method of sealing a lost circulation zone of a wellboremay include introducing a spacer fluid into the lost circulation zoneand introducing a LCM composition into the lost circulation zone. Thespacer fluid may provide separation between the drilling fluidpreviously in the wellbore and lost to the lost circulation zone and theLCM composition, which may be incompatible with the drilling fluid. Insome embodiments, a washer fluid may be introduced to the lostcirculation zone prior to introducing the spacer fluid to the lostcirculation zone. The method may further include introducing adisplacement fluid to the wellbore and formation after the LCMcomposition to displace the LCM composition into the formation. The LCMcomposition may include any of the epoxy resins, curing agents,weighting agents, accelerators, or other additives previously describedin this disclosure. The method may further include curing the LCMcomposition to form a cured LCM composition sealing the lost circulationzone. After curing, the lost circulation zone may be isolated from theother portions of the wellbore by the cured LCM composition.

In some embodiments, the spacer fluid, LCM composition, or both may beintroduced to the lost circulation zone by injecting the spacer fluid,LCM composition, or both into the formation at the lost circulationzone. In some embodiments, injection of the spacer fluid, LCMcomposition, or both may be accomplished by the process of “squeezing”the spacer fluid, LCM composition, or both into the formation. In someembodiments, the spacer fluid, the LCM composition, or both may beintroduced to the lost circulation zone through the drill stringdisposed within the wellbore. In some embodiments, the spacer fluid, theLCM composition or both may be introduced to the lost circulation zonethrough the drill bit of the drill string. In some embodiments, the lostcirculation zone is a low-injectivity zone.

Once the LCM composition has cured into a solid, drilling the wellboremay re-commence. In some embodiments, the drill string and drill may beused to drill through at least a portion of the LCM composition tocontinue drilling the wellbore.

Test Methods

Viscosity

The viscosity of the sealing compositions or LCM compositions may bemeasured using a standard oilfield viscometer, such as a FANN® Model 35viscometer manufactured by Fann Instrument Company for example,according to test methods provided in the API Recommended Practice ForCementing (RP 10B). The viscosity is reported as shear stress in unitsof pounds of force per 100 square feet (lbf/100 ft²). The viscometer mayalso be used to measure the shear rate of the sealing compositions orLCM compositions.

Gel Strength

The gel strength refers to the shear stress of the sealing compositionor LCM composition measured at a reduced shear rate following a definedperiod of time during which the sealing composition is maintained in astatic state. The shear stress of the composition at reduced shear ratemay be measured using a standard oilfield viscometer, such as a FANN®Model 35 viscometer operated at reduced rpms, such as at 3 rpm,according to the test methods described in API Recommended Practice OnDetermining the Static Gel Strength of Cement Formulations (RP 10B-6/ISO10426-6:2008). To measure the gel strength, the sealing composition orLCM composition is first stirred by contacting the composition with thespindle of the viscometer and operating the viscometer at 600 rotationsper minute (rpm). The viscometer is then turned off for a period of time(time period). For a 10-second gel strength, the time period is 10seconds, and for a 10-minute gel strength, the time period is 10minutes. It should be understood that other time periods for measuringgel strength may be used as reference times for measurements of gelstrength. During the time period, the composition comes to rest in astatic state. Upon expiration of the time period, the viscometer isturned back on at a reduced speed, such as 3 rpm for example, togenerate a reduced shear rate. The viscometer reading is then taken. Thegel strength of the sealing composition or LCM composition is reportedin units of pounds of force per 100 square feet (lbf/100 ft²).

Plastic Viscosity and Yield Point

The rheology of the sealing compositions and LCM compositions may bemodeled based on Bingham plastic flow behavior. In particular, thesealing compositions and LCM compositions may behave as a rigid body atlesser shear stress but flow as a viscous fluid at greater shear stress.The rheological behavior of the compositions may be determined bymeasuring the shear stress on the composition at different shear rates,which may be accomplished by measuring the shear stress, the shear rate,or both on the composition using a FANN® Model 35 viscometer operated at3 rpm, 6 rpm, 100 rpm, 200 rpm, 300 rpm, or 600 rpm, for example. Therheology of the sealing composition or LCM composition may be evaluatedfrom the plastic viscosity (PV) and the yield point (YP), which areparameters from the Bingham plastic rheology model. The PV is related tothe resistance of the composition to flow due to mechanical interactionbetween the solids of the composition and represents the viscosity ofthe composition extrapolated to infinite shear rate. The PV reflects thetype and concentration of the solids, such as weighting materials, inthe sealing composition or LCM composition, and a lesser PV ispreferred. The PV of the sealing composition or LCM composition may beestimated by measuring the shear stress of the composition using a FANN®Model 35 viscometer at spindle speeds of 300 rotations per minute (rpm)and 600 rpm and subtracting the 300 rpm viscosity measurement from the600 rpm viscosity measurement according to Equation 3 (EQU. 3), which issubsequently provided. The PV values determined for the sealingcompositions and LCM compositions are provided in this disclosure inunits of centipoise (cP).

PV=(viscosity at 600 rpm)−(viscosity at 300 rpm)  EQU. 3

At shear stress less than the YP of the sealing composition, the sealingcomposition behaves as a rigid body, and at shear stress greater thanthe YP of the sealing composition, the sealing composition flows as aviscous fluid. In other words, the YP represents the amount of stressrequired to move a fluid from a static condition. The YP is determinedby extrapolating the Bingham plastic rheology model to a shear rate ofzero. The YP of the sealing composition or the LCM composition may beestimated from the PV from EQU. 3 by subtracting the PV from the shearstress measured at 300 rpm according to Equation 4 (EQU. 4), which isprovided subsequently.

YP=(300 rpm reading)−PV  EQU. 4

The YP is expressed as a force per area, such as pounds of force per onehundred square feet (lbf/100 ft²) for example. The methods for measuringand determining PV and YP for the sealing compositions are consistentwith methods conventionally used for drilling fluids in general.

Shear Bond Test

A shear bond test determines the force required to move a pipe through acolumn of set cement or a sealing composition. This shear bond strengthcan be used to determine the length of pipe a column of set cement orsealing composition can support. The shear bond test includes filling anannulus between two pieces of pipe with a cement slurry or a sealingcomposition and letting it set. After the cement or sealing compositionsets, the outer pipe is supported on the bottom platen of a load presswhile force is applied to the center pipe by the load press. The loadindication on the press increases until the bond breaks between the pipeand the cement or sealing composition. This loading force is convertedto a force per unit area and is called the shear bond strength.

Preparing the Shear Bond Test Mold: The shear bond mold includes abottom pipe-centering device, an outer sleeve, an inner pipe, and a topcentering device. When assembled, the shear bond mold defines an annularspace between the outer sleeve and the inner pipe. All pieces of theshear bond test mold are thoroughly cleaned before assembling the piecesfor testing. Care should be taken to make sure the inner pipe and theouter sleeve do not have any mold release agents, such as oil or grease,in the areas in which the cement or sealing composition will contact.After cleaning, the bottom pipe-centering device is installed in thebottom of the outer sleeve. 0-rings may be used to seal the inner pipeand the outer sleeve. The inner pipe is installed in the bottompipe-centering device and aligned with the outer sleeve such that theinner pipe and the outer sleeve are concentric.

Filling the Test Mold: The cement or sealing composition is prepared andmixed according to standard American Petroleum Institute (API)procedures (or appropriate procedures for specialized slurries). Thecement or sealing composition, in the form of a slurry, is then pouredinto the annular space between the inner and outer pipe, while slowlystirring the slurry with a spatula to minimize the possibility ofsettling. The slurry is then puddled with a glass rod or spatula toremove any trapped air and the top centering device is placed on top ofthe slurry and in contact with the inner pipe and outer sleeve to centerthe inner pipe with respect to the outer sleeve. The bottom centeringdevice and the top centering device cooperate to maintain the inner pipecenter relative to the outer sleeve while the cement or sealingcomposition cures or sets.

Curing the Slurry: The shear bond test mold filled with the cement orsealing composition slurry is then placed in the curing medium, whichcan be a water bath or a pressure-curing chamber. The cement or sealingcomposition is then cured according to the appropriate test conditionsin the same manner as for curing a compressive strength specimen. Beforethe end of the curing time, the test specimens are removed from thewater bath, one at a time and, as quickly as possible, perform thefollowing: (1) remove the top centering device from the curing mold; (2)remove the bottom centering device from the mold; (3) determine theheight of the cement or sealing composition in contact with the innerpipe; and (4) place the test specimen back into the water bath and letthe temperature stabilize for approximately 30 minutes before testingfor shear bond strength. At the end of the curing period, the specimenshould be maintained at the lesser of the curing temperature or atemperature of from 170 degrees Fahrenheit (° F.) (77 degrees Celsius (°C.)) to 190° F. (88° C.) until the specimen is tested. The specimenshould not be allowed to cool to room temperature, because cooling toroom temperature may cause thermal shrinkage of the specimen and mold,which can alter the test results. If the specimen is cured using apressure-curing vessel, the pressure-curing vessel can be cooled to atemperature of from 170° F. (77° C.) and 190° F. (88° C.) and, ifnecessary, the test specimens can be removed from the pressure-curingvessel and placed into a water bath of the same temperature until thetime of testing.

Testing for Shear Bond Strength: The press is adjusted so that thespecimen fits between the top and bottom loading platens of the press.The test specimen is removed from the water bath and quickly placedbetween the loading platens with the outer sleeve in contact with thebottom loading platen and the inner pipe in contact with the upperloading platen. A loading force is applied to the test specimen by thepress at a uniform rate (as in testing for compressive strength). Whenthe shear bond breaks, the inner pipe moves downward through the setcement or sealing composition and the loading force begins to decrease.The maximum force reached before the pipe moved and the force began todecrease is recorded and used to determine the shear bond strength.

The cement contact area is determined using Equation 5 (EQU. 5), whichis subsequently provided in this disclosure.

CCA=CCH×π×D  EQU. 5

In EQU. 5, CCA is the cement contact area in inches squared (in²), CCHis the cement contact height on the pipe in inches (in), and D is thediameter of the pipe in inches (in). The diameter D in EQU. 5 willnormally be the outside diameter of the inner pipe, however, if movementoccurs between the set cement or sealing composition and the outersleeve, the inside diameter of the outer sleeve may also be usedcalculating the cement contact area. The shear bond strength may then becalculated from Equation 6 (EQU. 6), which is subsequently provided inthis disclosure.

$\begin{matrix}{{SBS} = \frac{MF}{CCA}} & {{EQU}.\mspace{14mu} 6}\end{matrix}$

In EQU. 6, SBS is the shear bond strength in pounds per square inch(psi), MF is the maximum force applied to the test specimen in pounds offorce (lbf), and CCA is the cement contact area in inches squaredcalculated from EQU. 5.

EXAMPLES

The following examples illustrate one or more features of the presentdisclosure. It should be understood that these examples are not intendedto limit the scope of the disclosure or the appended claims in anymanner. In these Examples, four epoxy resins were evaluated for use inthe sealing compositions described in the present disclosure. Table 1 issubsequently included in this disclosure and provides a cross-referencefor the epoxy resins utilized.

TABLE 1 Cross-Reference of Epoxy Resins Epoxy Resin ID Epoxy Resin NameResin 1 bisphenol-A-epichlorohydrin epoxy resin with the reactivediluent oxirane mono [(C12-C14)- alkyloxy)methyl] derivatives Resin 22,3-epoxypropyl-o-tolyl ether Resin 3 C12-C14 alkyl glycidyl ether Resin4 1,6-hexanediol diglycidyl ether

Example 1: Rheological Properties of Epoxy Resins

Resins 1 through 4 were evaluated for rheological properties accordingto the test methods previously described in this disclosure. Therheological properties of the four resins were measured for each resinindividually without addition of the curing agent, weighting material,or other additives. The rheological properties measured for Resins 1through 4 are shown in Table 2, which is subsequently provided in thisdisclosure.

TABLE 2 Rheological Properties of Resins 1 Through 4 RheologicalProperty Resin 1 Resin 2 Resin 3 Resin 4 Shear Stress at 600 rpm 385 1919.9 46 (lbf/100 ft²) Shear Stress at 300 rpm 384.6 10 10.3 23.5(lbf/100 ft²) Shear Stress at 200 rpm 384.4 6.5 6.6 15.4 (lbf/100 ft²)Shear Stress at 100 rpm 311.5 3.3 3.5 7.7 (lbf/100 ft²) Shear Stress at6 rpm 19.1 0.2 0.2 0.3 (lbf/100 ft²) Shear Stress at 3 rpm 9.6 0.2 0.20.2 (lbf/100 ft²) 10-second Gel Strength 9.5 0.1 0.2 0.2 (lbf/100 ft²)10-Minute Gel Strength 9.4 0.1 0.1 0.1 (lbf/100 ft²) PV (cP) 0.4 9 9.622.5 YP (lbf/ft²) 384.2 1 0.7 1

As shown in Table 2, Resin 2, Resin 3, and Resin 4 exhibited lesserrheology as shown by the shear stress values of less than 25 lbf/100 ft²over the range of 3 rpm to 600 rpm for Resins 2, 3, and 4. In contrast,Resin 1 exhibited greater rheology as shown by the increased shearstress values measured over the range of 3 rpm to 600 rpm. Resin 1 alsoexhibited 10-second and 10-minute gel strengths and yield point thatwere greater than the 10-second and 10-minute gel strengths and yieldpoint for Resins 2, 3, and 4. As demonstrated by the results in Table 2,the properties of the sealing compositions, LCM compositions, or bothmay be adjusted by adding or substituting different epoxy resins intothe sealing compositions or LCM compositions.

Example 2: Resin 4 with TEPA Curing Agent

In Example 2, Resin 4 was mixed with different quantities of the curingagent TEPA (tetraethylenepentamine) to evaluate the curing time requiredfor sealing compositions comprising Resin 4 and TEPA to change from aliquid phase to a solid or semi-solid phase. A quantity of 100 grams ofResin 4 at 200 degrees Fahrenheit (° F.) (93.3 degrees Celsius (° C.))was added to each of three containers. Quantities of 3 grams, 5.5 grams,and 6 grams of TEPA curing agent were added to the 100 grams of Resin 4in one of each of the three containers, and the contents of eachcontainer were thoroughly mixed. The mixtures were heated using a hotroll to maintain the temperatures of the mixtures at 200° F. (93.3° C.).Changes in the color, phase, and hardness of each of the mixtures wereobserved over time. Observations of phase and hardness are subsequentlyprovided in Table 3. The estimated cure times are provided in units ofhours (hrs) and minutes (min) throughout these Examples.

TABLE 3 Observations During Cure Time for Resin 4 with TEPA Curing AgentSam- Quantity ple Curing Quantity of of Curing ID Resin agent Resin (g)Agent (g) Observation 2A Resin 4 TEPA 100 3 Liquid after 8 hrs, semi-solid after a week 2B Resin 4 TEPA 100 6 Semi-solid after 4 hrs 38 min2C Resin 4 TEPA 100 5.5 Liquid after 8 hrs

It was observed that each of the mixtures turned darker in color andbecame thicker in viscosity as time progressed. Each of Samples 2A-2Cultimately cured to a solid sealing composition. As indicated in Table3, the cure time to cure the mixtures of Resin 4 and TEPA curing agentdecreased with increasing quantities of the TEPA curing agent added toResin 4. Sample 2A having 3 grams of TEPA was liquid after 8 hours andcured to a rubbery solid after a week. Sample 2B having 6 grams of TEPAcured to a semi-solid state in 4 hours and 38 minutes. For Sample 2C,the amount of TEPA was reduced slightly to 5.5 grams, which resulted inSample 2C remaining a liquid after 8 hours. Sample 2C eventually curedinto a solid sealing composition.

Example 3: Resin 4 and IPDA Curing Agent

In Example 3, Resin 4 was mixed with different quantities of IPDA(isophoronediamine) curing agent to evaluate the curing time requiredfor sealing compositions comprising Resin 4 and IPDA to change from aliquid phase to a solid or semi-solid phase. A quantity of 100 grams ofResin 4 at 200° F. (93.3° C.) was added to each of six containers.Quantities of 5 grams, 10 grams, 11 grams, 12 grams, 13, grams, and 14grams of IPDA curing agent were added to the 100 grams of Resin 4 in oneof each of the six containers, and the contents of each container werethoroughly mixed. The mixtures were heated using a hot roll to maintainthe temperatures of the mixtures at 200° F. (93.3° C.). Changes in thecolor, phase, and hardness of each of the mixtures were observed overtime. Observations of phase and hardness are subsequently provided inTable 4.

TABLE 4 Observations During Cure Time for Resin 4 with IPDA Curing AgentSam- Quantity ple Curing Quantity of of Curing ID Resin agent Resin (g)Agent (g) Observation 3A Resin 4 IPDA 100 10 Liquid after 8 hrs, changein color 3B Resin 4 IPDA 100 5 Liquid after 8 hrs, change in color 3CResin 4 IPDA 100 11 Liquid after 8 hrs, thickness increases 3D Resin 4IPDA 100 12 Liquid after 8 hrs, thickness increases 3E Resin 4 IPDA 10013 Liquid after 8 hrs, thickness increases 3F Resin 4 IPDA 100 14 Liquidafter 8 hrs, thickness increases

For Samples 3A and 3B, the quantities of IPDA curing agent of 10 gramsand 5 grams, respectively, were observed to produce a color change inthe sealing compositions of Samples 3A and 3B after 8 hours. However,the amounts of the IPDA curing agent in Samples 3A and 3B did notproduce an observable difference in viscosity of the sealing compositionafter 8 hours. While the color changes of Samples 3A and 3B indicate theexistence of some degree of curing, the amounts of IPDA curing agent inSamples 3A and 3B did not fully cure the sealing composition within acure time of less than 8 hours. Samples 3A and 3B eventually cured to arubbery solid within a cure time of 24 hours.

For Samples 3C through 3F, the amount of IPDA curing agent wasprogressively increased from 11 grams in Sample 3C to 14 grams in Sample3F. Sample 3C having 11 grams of IPDA curing agent per 100 grams ofresin exhibited an observable thickening of the sealing compositionafter 8 hours of cure time. Samples 3D, 3E, and 3F also exhibitedthickening of the sealing composition after 8 hours. However, Samples 3Cthrough 3F did not fully cure to a semi-solid or solid composition after8 hours of cure time. Thus, for a sealing composition comprising Resin 4with IPDA as the curing agent, more than 14 grams of the IPDA curingagent per 100 grams of Resin 4 may be required to cure the sealingcomposition to at least a semi-solid composition in less than 12 hours.

Example 4: Resin 4 and DETA Curing Agent

In Example 4, Resin 4 was mixed with different quantities of DETA(diethylenetriamine) curing agent to evaluate the curing time requiredfor sealing compositions comprising Resin 4 and DETA to change from aliquid phase to a solid or semi-solid phase. A quantity of 100 grams ofResin 4 at 200° F. (93.3° C.) was added to each of six containers.Quantities of 3 grams, 5 grams, 7 grams, 7.5 grams, 8 grams, and 9 gramsof IPDA curing agent were added to the 100 grams of Resin 4 in one ofeach of the six containers, and the contents of each container werethoroughly mixed. The mixtures were heated using a hot roll to maintainthe temperatures of the mixtures at 200° F. (93.3° C.). Changes in thecolor, phase, and hardness of each of the mixtures were observed overtime. Observations of phase and hardness are subsequently provided inTable 5.

TABLE 5 Observations During Cure Time for Resin 4 with DETA Curing AgentSam- Quantity ple Curing Quantity of of Curing ID Resin agent Resin (g)Agent (g) Observation 4A Resin 4 DETA 100 3 Liquid after 8 hrs 4B Resin4 DETA 100 5 Liquid after 8 hrs 4C Resin 4 DETA 100 7 Semi-solid after 6hrs and 10 min 4D Resin 4 DETA 100 7.5 Semi-solid after 4 hrs and 50 min4E Resin 4 DETA 100 8 Semi-solid after 4 hrs 4F Resin 4 DETA 100 9Semi-solid after 3 hrs

Samples 4A and 4B having 3 grams and 5 grams of DETA, respectively, wereobserved to be a liquid after a cure time of 8 hours. Therefore, theamounts of DETA in Samples 4A (3 grams) and 4B (5 grams) did not enableResin 4 to cure to a semi-solid or solid in less than or equal to 8hours. Samples 4A and 4B were observed to cure into a rubbery solidafter a cure time of 24 hours. For Samples 4C-4F, the amounts of DETAadded to Resin 4 were progressively increased from 7 grams to 9 grams.Sample 4C having 7 grams of DETA curing agent was observed to cure intoa semi-solid composition after 6 hours and 10 minutes. Samples 4D-4Fhaving 7.5 grams, 8 grams, and 9 grams of DETA, respectively, exhibiteddecreasing cure times to produce the semi-solid composition as thequantity of DETA was increased. Thus, it is observed that a sealingcomposition that includes Resin 4 and DETA as the curing agent may havean amount of DETA curing agent greater than 5 grams per 100 grams ofResin 4, without adding an accelerator. For example, the sealingcomposition may include Resin 4 and greater than or equal to 7 gramsDETA curing agent per 100 grams of Resin 4. As the amount of DETA curingagent increases, the curing time decreases.

Example 5: Resin 4 and TETA

In Example 5, Resin 4 was mixed with different quantities of TETA(triethylenetetramine) curing agent to evaluate the curing time requiredfor sealing compositions comprising Resin 4 and TETA to change from aliquid phase to a solid or semi-solid phase. A quantity of 100 grams ofResin 4 at 200° F. (93.3° C.) was added to each of five containers.Quantities of 2 grams, 3 grams, 4 grams, 5 grams, and 5.5 grams of TETAcuring agent were added to the 100 grams of Resin 4 in one of each ofthe five containers, and the contents of each container were thoroughlymixed. The mixtures were heated using a hot roll to maintain thetemperature of the mixtures at 200° F. (93.3° C.). Changes in the color,phase, and hardness of each of the mixtures were observed over time.Observations of phase and hardness are subsequently provided in Table 6.

TABLE 6 Observations During Cure Time for Resin 4 with TETA Curing AgentSam- Quantity ple Curing Quantity of of Curing ID Resin agent Resin (g)Agent (g) Observation 5A Resin 4 TETA 100 2 Liquid after 8 hrs,thickness increases 5B Resin 4 TETA 100 3 Liquid after 8 hrs, thicknessincreases 5C Resin 4 TETA 100 4 Liquid after 8 hrs, thickness increases5D Resin 4 TETA 100 5 Liquid after 8 hrs, thickness increases 5E Resin 4TETA 100 5.5 Semi-solid after 5 hrs and 45 min

For Samples 5A-5D, the amount of TETA curing agent per 100 grams ofResin 4 was increased from 2 grams to 5 grams. Samples 5A-5D were allliquids after a cure time of 8 hours, but each of Samples 5A-5Dexhibited observable thickening of the sealing composition comprisingResin 4 and TETA. Samples 5A-5D were observed to cure to a rubbery solidafter a cure time of more than 12 hours. Sample 5E included 5.5 grams ofTETA per 100 grams of Resin 4 and cured to a semi-solid compositionafter a cure time of 5 hours and 45 minutes. Therefore, it is observedthat a sealing composition comprising Resin 4 and TETA curing agent mayhave greater than 5 grams TETA per 100 grams of Resin 4, or greater thanor equal to 5.5 grams TETA per 100 grams of Resin 4, for the sealingcomposition to cure to at least a semi-solid composition in less than 8hours without adding an accelerator.

The combination of Resin 4 and the TETA curing agent of Example 5resulted in a faster rate of cure of the epoxy resin and a lesser curetime compared to combinations of Resin 4 with TEPA, IPDA, or DETA inExamples 2, 3, and 4, respectively. As previously discussed, thecombination of Resin 4 with only 5.5 grams of TETA in Example 5 curedthe sealing composition to a semi-solid composition in less than 6hours. In comparison, the sealing composition of Example 2, inparticular Sample 2C that included Resin 4 and 5.5 grams of TEPA, wasstill a liquid after 8 hours of curing. For the combination of Resin 4and TEPA curing agent of Example 2, 6 grams TEPA per 100 grams of Resin4 resulted in curing Resin 4 to a semi-solid composition in less than 8hours.

Example 6: Resin 1 and TEPA Curing Agent

In Example 6, Resin 1 was mixed with different quantities of TEPA(tetraethylenepentamine) curing agent to evaluate the curing timerequired for sealing compositions comprising Resin 1 and TEPA to changefrom a liquid phase to a solid or semi-solid phase. A quantity of 100grams of Resin 1 at 200° F. (93.3° C.) was added to each of fourcontainers. Quantities of 1 gram, 2 grams, 3 grams, and 3.5 grams ofTEPA curing agent were added to the 100 grams of Resin 1 in one of eachof the four containers, and the contents of each container werethoroughly mixed. The mixtures were heated using a hot roll to maintainthe temperature of the mixtures at 200° F. (93.3° C.). Changes in thecolor, phase, and hardness of each of the mixtures were observed overtime. Observations of phase and hardness are subsequently provided inTable 7.

TABLE 7 Observations During Cure Time for Resin 1 with TEPA Curing AgentSam- Quantity ple Curing Quantity of of Curing ID Resin agent Resin (g)Agent (g) Observation 6A Resin 1 TEPA 100 1 Color changed, liquid after6 hrs 6B Resin 1 TEPA 100 2 Color changed, liquid after 8 hrs 6C Resin 1TEPA 100 3 Color changed, thickness increased after 8 hrs 6D Resin 1TEPA 100 3.5 Color changed, semi-solid after 4 hrs

For Samples 6A and 6B, the quantities of TEPA curing agent of 1 gram and2 grams, respectively, were observed to produce a color change in thesealing compositions of Samples 6A and 6B after 6 hours and 8 hours,respectively. While the color change of Samples 6A and 6B indicates theexistence of some degree of curing of the Resin 1, the amounts of TEPAcuring agent in Samples 6A and 6B were did not produce an observablechange in viscosity or cure Resin 1 into a semi-solid or solidcomposition in 8 hours or less. Samples 6A and 6B were observed to cureto a rubbery solid after a cure time of 12 hours.

For Sample 6C, the amount of TEPA was increased to 3 grams per 100 gramsof Resin 1, which resulted in a change in color as well as an observableincrease in the thickness (viscosity) of Resin 1 after a cure time of 8hours. Increasing the amount of TEPA to 3.5 grams per 100 grams of Resin1 in Sample 6D resulted in curing Resin 1 to a semi-solid compositionafter a cure time of 4 hours.

Example 7: Resin 1 and DETA Curing Agent

In Example 7, Resin 1 was mixed with different quantities of DETA(diethylenetriamine) curing agent to evaluate the curing time requiredfor sealing compositions comprising Resin 1 and DETA to change from aliquid phase to a solid or semi-solid phase. A quantity of 100 grams ofResin 1 at 200° F. (93.3° C.) was added to each of three containers.Quantities of 3 grams, 5 grams, and 7 grams of DETA curing agent wereadded to the 100 grams of Resin 1 in one of each of the threecontainers, and the contents of each container were thoroughly mixed.The mixtures were heated using a hot roll to maintain the temperature ofthe mixtures at 200° F. (93.3° C.). Changes in the color, phase, andhardness of each of the mixtures were observed over time. Observationsof phase and hardness are subsequently provided in Table 8.

TABLE 8 Observations During Cure Time for Resin 1 with DETA Curing AgentSam- Quantity ple Curing Quantity of of Curing ID Resin agent Resin (g)Agent (g) Observation 7A Resin 1 DETA 100 3 Semi-solid after 6 hrs and20 min 7B Resin 1 DETA 100 5 Semi-solid after 2 hrs and 15 min, solidafter 24 hours 7C Resin 1 DETA 100 7 Semi-solid after 1 hr and 10 min,solid after 8 hrs

In Sample 7A, the combination of 100 grams of Resin 1 with 3 grams ofDETA curing agent was observed to cure Resin 1 to a semi-solidcomposition after 6 hours and 20 minutes and to a rubbery solid after acure time of 8 hours. As the amount of DETA curing agent is increased to5 grams DETA per 100 grams of Resin 1 in Sample 7B and 7 grams DETA per100 grams of Resin 1 in Sample 7C, the cure time needed to cure Resin 1to a semi-solid composition, rubbery solid, or rigid solid compositiondecreases. As shown be the results for Sample 7A, a sealing compositionthat includes Resin 1 and DETA curing agent may need less than 5 gramsof DETA, or even as little as 3 grams of DETA, to cure the sealingcomposition within a cure time of less than 12 hours, or even less than8 hours, without including an accelerator.

Examples 8-11: Resin 2 and Various Curing Agents

In Examples 8-11, Resin 2 was mixed with different quantities of DETA(diethylenetriamine), TETA (triethylenetetramine), TEPA(tetraethylenepentamine), IPDA (isophoronediamine) curing agents toevaluate the curing time required for the various sealing compositionsto change from a liquid phase to a solid or semi-solid phase. ForExample 8, a quantity of 100 grams of Resin 2 at 200° F. (93.3° C.) wasadded to each of two containers. Quantities of 7 grams and 9 grams ofDETA curing agent were added to the 100 grams of Resin 2 to each of thetwo containers, respectively. For Example 9, a quantity of 100 grams ofResin 2 at 200° F. (93.3° C.) was added to each of three containers.Quantities of 5.5 grams, 6 grams, and 8 grams of TETA curing agent wereadded to the 100 grams of Resin 2 to each of the three containers,respectively. For Example 10, a quantity of 100 grams of Resin 2 at 200°F. (93.3° C.) was added to each of two containers. Quantities of 15grams and 20 grams of IPDA curing agent were added to the 100 grams ofResin 2 to each of the two containers, respectively. For Example 11, aquantity of 100 grams of Resin 2 at 200° F. (93.3° C.) was added to eachof two containers. Quantities of 7 grams and 10 grams of TEPA curingagent were added to the 100 grams of Resin 2 to each of the twocontainers, respectively.

The contents of each container of Examples 8-11 were thoroughly mixed.The mixtures of Examples 8-11 were heated using a hot roll to maintainthe temperature of the mixtures at 200° F. (93.3° C.). Changes in thecolor, phase, and hardness of each of the mixtures of Examples 8-11 wereobserved over time. Observations of phase and hardness for Examples 8-11are subsequently provided in Table 9.

TABLE 9 Observations During Cure Time for Resin 2 with DETA (Example 8),TETA (Example 9), IPDA (Example 10), and TEPA (Example 11) Sam- Quantityple Curing Quantity of of Curing ID Resin agent Resin (g) Agent (g)Observation  8A Resin 2 DETA 100 7 Liquid after 8 hrs  8B Resin 2 DETA100 9 Liquid after 8 hrs  9A Resin 2 TETA 100 6 Liquid after 8 hrs  9BResin 2 TETA 100 5.5 Liquid after 8 hrs  9C Resin 2 TETA 100 8 Liquidafter 8 hrs 10A Resin 2 IPDA 100 20 Liquid after 8 hrs 10B Resin 2 IPDA100 15 Liquid after 8 hrs 11A Resin 2 TEPA 100 10 Liquid after 8 hrs 11BResin 2 TEPA 100 7 Liquid after 8 hrs

The compositions of Examples 8-11 cured to solid sealing compositionsfollowing additional cure time beyond eight hours. However, thecompositions of Examples 8-11 that included Resin 2 included greaterquantities of the curing agent to cure to a semi-solid state compared tothe sealing compositions of Examples 1-7 that included Resin 1 or Resin4.

Examples 12: Comparison of Resin 1 to a Mixture of Resin 1 and Resin 4

For Example 12, a sealing composition that included Resin 1 and TEPAcuring agent was compared to a sealing composition that included amixture of Resin 1 and Resin 4 with TEPA curing agent. For Sample 12A,100 grams of Resin 1 at 200° F. (93.3° C.) was added to a container. 10grams of TEPA curing agent and 24.63 grams of a weighting agent wereadded to the 100 grams of Resin 1 in the container. The weighting agentwas manganese oxide (Mn₃O₄) and was added to adjust the density ofSample 12A so a measured density of 80 pounds per cubic foot (pcf). ForSample 12B, 80 grams of Resin 1 and 20 grams of Resin 4 at 200° F.(93.3° C.) were added to a container. 10 grams of TEPA curing agent wasadded to the mixture of Resin 1 and Resin 2 in the container. An amountof Mn₃O₄ weighting agent was added to adjust the density of Sample 12Bto 80 pcf. A total amount of Mn₃O₄ added to Sample 12B was 26.10 grams.

The mixtures of Samples 12A and 12B were thoroughly mixed. The mixturesof Samples 12A and 12B were heated using a hot roll to maintain thetemperature of the mixtures at 200° F. (93.3° C.). The elapsed timeneeded for each of Samples 12A and 12B to turn from a liquid to asemi-solid was measured. Changes in the color, phase, and hardness ofeach of the mixtures were observed over time. The cure time to asemi-solid material and observations of phase and hardness for Samples12A and 12B are subsequently provided in Table 10.

TABLE 10 Observations During Cure Time for Resin 1 with TEPA CuringAgent Compared to a Mixture of Resin 1 and Resin 4 with TEPA CuringAgent. Quantity Quantity Quantity Weighting Time to Semi- Sample ofResin 1 of Resin 4 of TEPA Material solid State ID (g) (g) (g) (g) (min)Observations 12A 100 0 10 24.63 37 The mixture was solid after 9 hrs.The mixture was harder in the middle than at the edges 12B 80 20 1026.10 39 The mixture was solid after 9 hrs. The mixture was harder inthe middle than at the edges

As shown in Table 10, both Sample 12A and Sample 12B cured to asemi-solid state in less than 40 minutes. The replacement of 20 grams ofResin 1 with 20 grams of Resin 4 in Sample 12B slightly decreased thecuring rate, resulting in a slightly increased cure time compared toSample 12A, which included only Resin 1. Thus, the cure time may beadjusted by combining an amount of Resin 4 with Resin 1 in the sealingcomposition.

Example 13: Curing Time for Sealing Compositions Comprising Mixtures ofResin 1 and Resin 4 with DETA Curing Agent

For Example 13, sealing compositions comprising various mixtures ofResin 1 and Resin 2 were evaluated with different amounts of DETA curingagent. For Samples 13A, 13B, and 13C, 80 grams of Resin 1 and 20 gramsof Resin 4 at 200° F. (93.3° C.) were added to each of three containers.Quantities of 7 grams, 5 grams, and 3 grams of DETA curing agent wereadded to each of the three containers, respectively. For Samples 13D and13E, 50 grams of Resin 1 and 50 grams of Resin 4 at 200° F. (93.3° C.)were added to each of two containers. Quantities of 7 grams and 5 gramsof DETA curing agent were added to each of the two containers,respectively. For Samples 13F, 13G, and 13H, 30 grams of Resin 1 and 70grams of Resin 4 at 200° F. (93.3° C.) were added to each of threecontainers. Quantities of 7 grams, 5 grams, and 3 grams of DETA curingagent were added to each of the three containers, respectively.

The mixtures of Samples 13A-13H were thoroughly mixed. The mixtures ofSamples 13A-13H were heated using a hot roll to maintain the temperatureof the mixtures at 200° F. (93.3° C.). The elapsed time needed for eachof Samples 13A-13H to turn from a liquid to a semi-solid was measured inminutes (min). Changes in the color, phase, and hardness of each of themixtures were observed over time. The cure time to a semi-solid materialand observations of phase and hardness for Samples 13A-13H aresubsequently provided in Table 11.

TABLE 11 Observations During Cure Time for Various Mixtures of Resin 1and Resin 4 with DETA Curing Agent. Quantity Quantity Quantity Time toSample of Resin of Resin of DETA Semi-solid ID 1 (g) 4 (g) (g) State(min) Observations 13A 80 20 7  72 Semi-solid after 1 hr and 12 min,solid after 8 hrs 13B 80 20 5 120 Semi-solid after 2 hrs, solid after 24hrs 13C 80 20 3 385 Semi-solid after 6 hrs and 25 min 13D 50 50 7 130Semi-solid after 2 hr and 10 min 13E 50 50 5 260 Semi-solid after 4 hrsand 20 min, solid after 24 hrs 13F 30 70 7 170 Semi-solid after 2 hrsand 50 min, hard rubber after 8 hrs 13G 30 70 5 170 Semi-solid after 2hrs and 50 min, solid after 24 hrs 13H 30 70 3  480+ Liquid after 8 hrs

As shown in Table 11, the curing time increases as the weight ratio ofResin 1 to Resin 4 decreases. As previously observed, the cure timeincrease with increasing quantities of the curing agent. Samples 13C,13E, and 13H had curing times to transition from a liquid to asemi-solid of greater than 4 hours. This makes the sealing compositionsof Samples 13C, 13E, and 13H more suited to primary sealing of thewellbore annulus or casing-casing annuli. Samples 13C, 13E, and 13H mayalso be used in remedial actions to repair the wellbore. Samples 13A,13B, 13D, 13F, and 13G had curing times to transition from a liquid to asemi-solid of less than 4 hours. These sealing compositions may besuited for use as lost circulation materials for remediating a lostcirculation in a wellbore due to the reduced cure times compared tocompositions with reduced proportions of the curing agent. Samples 13A,13B, 13D, 13F, and 13G may also be suited for remedial actions to repairthe wellbore.

Example 14: Thickening Time Test for Downhole Application of the SealingComposition to Remediate Increased Casing-Casing Annulus PressureCondition

In Example 14, a sealing composition was used in a “squeeze” operationto remediate a section of a wellbore exhibiting casing-casing annuluspressure increase. A sealing composition comprising 77 wt. % Resin 1, 19wt. % Resin 4, and 2 wt. % TEPA curing agent was prepared and mixed fora mixing time of 30 minutes. The remediation area was at a depth of12,000 feet below the surface. The sealing composition was pumped downthe wellbore and squeezed into the remediation area. During thesqueezing operation, the bottom hole circulating temperature (BHCT) was223° F. (106° C.), and the bottom hole static temperature (BHST) was260° F. (127° C.). The pressure was ramped up over a period of 30minutes to a final pressure of 5700 pounds per square inch (psi) (39,300kilopascals). The thickening time of the sealing composition was 4 hoursand 15 minutes. The final Bearden consistency of the sealing compositionwas 100 Be. The thickening time and Bearden consistency were measuredusing a high temperature high pressure (HTHP) consistometer obtainedfrom Chandler Engineering. It was observed that the sealing compositionremediated the weak zone in the remediation area to reduce the downholecasing-casing annulus pressure increase.

Comparative Example 15: Conventional Cement Composition

In Comparative Example 15, two samples of a conventional cementcomposition were prepared. The conventional cement composition includedPortland cement, silica, a weighting agent, an expanding additive, adefoamer, a latex additive and latex stabilizer, a fluid loss additive,a cement friction reducer, a cement retarder and water. The formulationfor the conventional cement composition of Comparative Example 15 isshown in Table 12, which is subsequently provided in this disclosure.Samples 15A and 15B were prepared using the same formulation of theconventional cement composition. The conventional cement compositions ofSamples 15A and 15B were 160 pounds per cubic foot (lbm/ft³) (2563kilograms per cubic meter (kg/m³), where 1 lbm/ft³ is equal to 119.8kg/m³).

Example 16: Sealing Composition Including the Epoxy Resin System andConstituents of Conventional Cement

In Example 16, a sealing composition was prepared by replacing the latexand latex stabilizer of the conventional cement composition ofComparative Example 15 with the epoxy resin system and adjusting theformulation to achieve a density comparable to the conventional cementcompositions of Comparative Example 15. The epoxy resin in the sealingcomposition of Example 16 included a mixture ofbisphenyl-A-epichlorohydrin epoxy resin and butyl glycidyl ether, andthe curing agent was diethyl toluene diamine (DETDA). The formulationfor the sealing composition of Example 16 is shown in Table 12,subsequently provided in this disclosure. Two samples of the sealingcomposition of Example 16 (Samples 16A and 16B) were prepared using thesame formulation.

TABLE 12 Formulations for the conventional cement compositions ofComparative Example 15 and for the sealing composition of Example 16.All weights in Table 12 are provided in grams (g). Component 15A 15B 16A16B Portland Cement (g) 481.01 481.01 461.07 461.07 Silica powder (g)168.35 168.35 193.65 193.65 Weighting materials (g) 625.32 625.32 599.40599.40 Expanding additive (g) 4.81 4.81 13.83 13.83 Defoamer (g) 1.181.18 1.13 1.13 Latex additive (g) 42.58 42.58 — — Latex stabilizer (g)9.05 9.05 — — Fluid loss additive (g) 0.48 0.48 1.84 1.84 Cementfriction reducer (g) 3.85 3.85 4.61 4.61 Cement retarder (g) 5.29 5.294.97 4.97 Epoxy resin (g) — — 34.58 34.58 Curing agent (g) — — 9.34 9.34Water (g) 195.85 195.85 203.27 203.27 Total (g) 1537.77 1537.77 1527.691527.69 Density (lbm/ft³) 160 160 159 159

Example 17: Evaluation of the Impact of Adding Epoxy Resin System onElasticity, Compressive Strength, and Bond Strength of the SealingComposition

The conventional cement compositions of Comparative Example 15 and thesealing compositions of Example 16 were evaluated for compressivestrength and bond strength according to the shear bond test previouslydescribed in this disclosure. The results for the compressive strengthand shear bond strength of the conventional cement composition ofComparative Example 15 and the sealing composition of Example 16 areprovided subsequently in this disclosure in Table 13.

TABLE 13 Comparison of Compressive Strength and Shear Bond Strength forthe Conventional Cement Compositions of Comparative Example 15 and theSealing Compositions of Example 16. Cement Inside Maximum Sam- ContactDiameter Cement Force ple Height on of Outside Contact Applied to ShearBond No. Pipe (in) Pipe (in) Area (in²) Sample (lbf) Strength (psi) 15A3.99 2.5 31.32 11250 359 15B 3.88 2.5 30.45 12190 400 16A 3.81 2.5 29.9014230 476 16B 3.93 2.5 30.85 16700 541

As shown in Table 13, the sealing composition of Example 16 having theepoxy resin system added (e.g., average of Samples 16A and 16B)exhibited an average bond strength of 509 psi, which was significantlygreater than the average bond strength of 378 psi for the conventionalcement compositions of Comparative Example 15 (e.g., average of Samples15A and 15B). Additionally, the sealing compositions of Example 16having the epoxy resin system added (e.g., Samples 16A and 16B) wereable to withstand a greater amount of force (e.g., average of 15,465lbf) applied to the compositions compared to the conventional cementcompositions of Comparative Example 15 (e.g., Samples 15A and 15B),which were subjected to an average of 11,720 psi. Thus, the sealingcompositions having the epoxy resin system according to embodiments ofthe present disclosure are shown to exhibit greater compressive strengthand the shear bond strength compared to conventional cementcompositions.

The conventional cement compositions of Comparative Example 15 and thesealing compositions of Example 16 were also evaluated for bulk modulus.The sealing compositions of Example 16 having the epoxy resin systemadded (e.g., Samples 16A and 16B) exhibited a bulk modulus of about1,184,000 psi, which was less than the static bulk modulus of 1,404,000psi determined for the conventional cement compositions of ComparativeExample 15 (e.g., Samples 15A and 15B). Lesser bulk modulus indicatesthat the material exhibits greater elasticity. Thus, it has been shownin Example 17 that the sealing compositions of Example 16 having theepoxy resin system added exhibited greater elasticity compared to theconventional cement compositions of comparative Example 15.

It is noted that one or more of the following claims utilize the term“where” or “in which” as a transitional phrase. For the purposes ofdefining the present technology, it is noted that this term isintroduced in the claims as an open-ended transitional phrase that isused to introduce a recitation of a series of characteristics of thestructure and should be interpreted in like manner as the more commonlyused open-ended preamble term “comprising.” For the purposes of definingthe present technology, the transitional phrase “consisting of” may beintroduced in the claims as a closed preamble term limiting the scope ofthe claims to the recited components or steps and any naturallyoccurring impurities. For the purposes of defining the presenttechnology, the transitional phrase “consisting essentially of” may beintroduced in the claims to limit the scope of one or more claims to therecited elements, components, materials, or method steps as well as anynon-recited elements, components, materials, or method steps that do notmaterially affect the novel characteristics of the claimed subjectmatter. The transitional phrases “consisting of” and “consistingessentially of” may be interpreted to be subsets of the open-endedtransitional phrases, such as “comprising” and “including,” such thatany use of an open ended phrase to introduce a recitation of a series ofelements, components, materials, or steps should be interpreted to alsodisclose recitation of the series of elements, components, materials, orsteps using the closed terms “consisting of” and “consisting essentiallyof.” For example, the recitation of a composition “comprising”components A, B, and C should be interpreted as also disclosing acomposition “consisting of” components A, B, and C as well as acomposition “consisting essentially of” components A, B, and C. Anyquantitative value expressed in the present application may beconsidered to include open-ended embodiments consistent with thetransitional phrases “comprising” or “including” as well as closed orpartially closed embodiments consistent with the transitional phrases“consisting of” and “consisting essentially of.”

As used in the Specification and appended Claims, the singular forms“a”, “an”, and “the” include plural references unless the contextclearly indicates otherwise. The verb “comprises” and its conjugatedforms should be interpreted as referring to elements, components orsteps in a non-exclusive manner. The referenced elements, components orsteps may be present, utilized or combined with other elements,components or steps not expressly referenced.

It should be understood that any two quantitative values assigned to aproperty may constitute a range of that property, and all combinationsof ranges formed from all stated quantitative values of a given propertyare contemplated in this disclosure. The subject matter of the presentdisclosure has been described in detail and by reference to specificembodiments. It should be understood that any detailed description of acomponent or feature of an embodiment does not necessarily imply thatthe component or feature is essential to the particular embodiment or toany other embodiment. Further, it should be apparent to those skilled inthe art that various modifications and variations can be made to thedescribed embodiments without departing from the spirit and scope of theclaimed subject matter.

1. A composition for sealing an annulus of a wellbore, the compositioncomprising: from 20 weight percent to 97 weight percent epoxy resinbased on the total weight of the composition, the epoxy resin comprisingat least one of 2,3-epoxypropyl o-tolyl ether, alkyl glycidyl ethershaving from 12 to 14 carbon atoms, or a compound having formula (I):(OC₂H₃)—CH₂—O—R¹—O—CH₂—(C₂H₃O)  (1) where R¹ is a linear or branchedhydrocarbyl having from 4 to 24 carbon atoms; and from 1 weight percentto 20 weight percent curing agent based on the total weight of thecomposition.
 2. The composition of claim 1 where the curing agentcomprises at least one of tetraethylenepentamine (TEPA),diethylenetriamine (DETA), triethylenetetramine (TETA), orisophoronediamine (IPDA).
 3. The composition of claim 1 where the epoxyresin has an epoxy value of from 4.5 epoxy equivalents per kilogram to5.5 epoxy equivalents per kilogram.
 4. The composition of claim 1 wherethe epoxy resin has an epoxy equivalent weight of from 170 to 350 gramsper epoxy equivalent.
 5. The composition of claim 1 further comprisingan accelerator.
 6. The composition of claim 1 where the epoxy resinfurther comprises a reactive diluent.
 7. The composition of claim 6where the reactive diluent has the formula R—O—CH₂—(C₂H₃O), where R is ahydrocarbyl having from 12 to 14 carbon atoms.
 8. The composition ofclaim 1 where the composition has a cure time of from 4 hours to 12hours.
 9. The composition of claim 1 where the composition has a densityof from 55 pounds per cubic foot to 170 pounds per cubic foot.
 10. Thecomposition of claim 1 where the viscosity of the composition is from 1millipascal seconds (mPa·s) to 50,000 mPa·s.
 11. The composition ofclaim 1 where the epoxy resin comprises 2,3-epoxypropyl o-tolyl ether.12. The composition of claim 1 where the epoxy resin further comprisesfrom 0.1 weight percent to 80 weight percent bisphenol-A-epichlorohydrinepoxy resin based on the total weight of the epoxy resin in thecomposition.
 13. The composition of claim 1 where the epoxy resincomprises 1,6-hexanediol diclycidyl ether.
 14. The composition of claim1 where the epoxy resin comprises 1,6-hexanediol diclycidyl ether andbisphenol-A-epichlorohydrin epoxy resin.
 15. The composition of claim 1further comprising a weighting material.
 16. A composition for sealingan annulus of a wellbore, the composition comprising: from 20 weightpercent to 97 weight percent epoxy resin based on the total weight ofthe composition, the epoxy resin comprising bisphenol-A-epichlorohydrinepoxy resin modified with an oxirane mono [(C₁₂-C₁₄)-alkyloxy)methyl]derivative and a reactive diluent having formula R²—O—CH₂—(C₂H₃O), whereR² is hydrocarbyl having from 12 to 14 carbon atoms; and from 1 weightpercent to 20 weight percent curing agent based on the total weight ofthe composition.
 17. The composition of claim 16 where the epoxy resincomprises from 1 weight percent to 20 weight percent of the reactivediluent based on the total weight of the epoxy resin in the composition.18. The composition of claim 16 where the epoxy resin further comprisesat least one of 2,3-epoxypropyl o-tolyl ether, alkyl glycidyl ethershaving from 12 to 14 carbon atoms, or a compound having formula (I):(OC₂H₃)—CH₂—O—R¹—O—CH₂—(C₂H₃O)  (1) where R¹ is a linear or branchedhydrocarbyl having from 4 to 24 carbon atoms.
 19. The composition ofclaim 16 where the curing agent comprises at least one oftetraethylenepentamine (TEPA), diethylenetriamine (DETA),triethylenetetramine (TETA), or isophoronediamine (IPDA).
 20. Thecomposition of claim 16 where the epoxy resin comprises from 1 weightpercent to 80 weight percent 1,6-hexanediol diclycidyl ether based onthe total weight of the epoxy resin in the composition. 21-26.(canceled)